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• RFe 2 Si 2 (R = Ho, Tm) intermetallic compounds were successfully synthesized. • Ultra-low working temperature and large low-field magnetocaloric effect were obtained. • Good thermal and magnetic reversibility were confirmed based on the analysis of transition. • RFe 2 Si 2 (R = Ho, Tm) compounds show potential applications on low-temperature magnetic cooling. Nowadays, magnetic refrigerant technology has drawn much attention for its environmental friendliness. Those magnetic materials possessing giant low-field magnetocaloric effect (MCE) performance are of great importance for practical applications, especially at low temperatures. Herein, we present a detailed study on polycrystalline magnetocaloric compounds HoFe 2 Si 2 and TmFe 2 Si 2. HoFe 2 Si 2 exhibits a transition from antiferromagnetic to paramagnetic phase at 2.2 K, while no long-range magnetic ordering is observed in TmFe 2 Si 2 even temperature down to 2 K. For both compounds, they showed large low-field magnetic entropy change (−ΔS M) with the peak values of 10.6 and 7.9 J kg−1 K−1 under field change of 0–2 T for HoFe 2 Si 2 and TmFe 2 Si 2 , respectively, which is comparable or even larger than some low-temperature magnetocaloric materials. In addition, the characteristic of second-order magnetic transitions of both compounds were confirmed on basis of Arrott plots and mean-field theory criterion. The low magnetic ordering temperatures, large low-field MCE performance along with the feature of second order phase transition for HoFe 2 Si 2 and TmFe 2 Si 2 indicate that both compounds are promising candidate for magnetic refrigerant materials at liquid helium temperature. [ABSTRACT FROM AUTHOR]

This work investigates magnetic properties and the magnetocaloric effect in the scope of continuous and first-order phase transitions in different stability regimes of a system described by the Ashkin–Teller model. Mean Field Theory is implemented through the Gibbs–Bogoliubov variational principle to obtain expressions for free energy, entropy and magnetization, in addition to computing the magnetocaloric properties of the system under analysis. The starting point is a detailed analysis of magnetic properties as a function of temperature, coupling configurations and external fields. Continuous and first-order phase transitions are observed. The impact of having the system under the influence of an external field is studied, showing and discussing the most favorable conditions for the manifestation of the magnetocaloric potential. In addition, phase transitions between metastable and stable states due to the hysteresis effect when varying the external field are obtained from two different methods, Maxwell relations and the use of entropy variation to compute the correct magnetocaloric effect properties. • Study of the Magnetocaloric Effect in the Ashkin–Teller model. • Magnetizations as a function of temperature varying the external field. • Free energy as a function of magnetizations varying the external field. • Magnetocaloric Effect for the different phases present in the model. • Continuous and first-order phase transitions. [ABSTRACT FROM AUTHOR]

• The detrimental phase α-Fe in the equilibrium organization of the LaFe 11.6- x Ni x Si 1.4 (x = 0 ∼ 0.2) alloy is continuously refined, and the 1:13 main phase gradually increases. • The Curie temperature T C of the alloys increased from 228.68 K to 252.19 K with the Ni-doped content x = 0.2 at 1323 K. • The optimized annealing temperature also makes LaFe 11.6- x Ni x Si 1.4 (x = 0.2) alloy obtain the maximum magnetic entropy change 16.01 J/(kg⋅K) at 1343 K, which confirms it could be effectively modulated by optimizing the annealing process. Magnetic properties and magnetocaloric effect of LaFe 11.6- x Ni x Si 1.4 alloys upon Ni substitution have been systematically investigated. It was found that the substitution of Fe by Ni elements results in an increase in the Curie temperature T C , and affects the LaFe 11.6- x Ni x Si 1.4 (x = 0, 0.1, 0.2) alloys magnetocaloric properties. A maximum shift in the Curie temperature T C of about 8.97 K compared with the base compound (x = 0). Through equilibrium organization analysis, the partial substitution of Ni for Fe in LaFe 11.6- x Ni x Si 1.4 alloys promotes the formation of 1:13 phase and the elimination of impurity phases significantly. About heat treatment, the magnetic entropy change (−Δ S M) of LaFe 11.6- x Ni x Si 1.4 (x = 0.2) alloy annealed at 1343 K is 16.01 J/(kg⋅K) under a 2.5 T magnetic field. This indicates that optimizing the annealing temperature can beneficially accelerate the eutectic reaction process and result in an increase in the 1:13 phase content, thereby enhancing its magnetocaloric properties. Therefore, the microstructure and magnetocaloric properties of LaFe 11.6- x Ni x Si 1.4 alloys could be effectively modulated by optimizing the annealing process, which provides a significant technical reference for the practical application near-room temperature magnetic refrigeration technology. [ABSTRACT FROM AUTHOR]

The compound Ca 2 MnTiO 6 , synthesized using a two-step solid-state reaction method, has been studied for its structural, spectroscopic (XPS) and magnetic properties, as part of our efforts to understand the correlation between mixed metal oxide bonds and magnetism in double perovskite oxides. Room temperature diffraction studies shows that the compound is in orthorhombic structure at room temperature and remains so till low temperatures, although the variation in global instability index (GII) indicated little instability of the structure as the temperature is lowered from room temperature (∼300 K) to 3 K. The compound exhibits interesting behavior in magnetic susceptibility, as it exhibits magnetization reversal or negative magnetic susceptibility at low applied fields which turns positive for higher fields. Magnetic susceptibility also exhibits two anomalies at T N1 ∼ 8.2 K and another one around, T N2 , between 121 – 124 K. Magnetization as a function of field reveals weak antiferromagnetism in the system, as M varies non-linearly, but sluggishly below T <150 K, with no signature of saturation with respect to H. Overall, magnetization studies show that there is inherent magnetic frustration in the system and lack of long-range magnetic order, which is supported by low temperature neutron diffraction studies too. The XPS studies quantify the oxidation states of mixed valent Mn and Ti. A comparison of the structural and physical properties of double perovskite compound is presented here to understand the strong correlation between structural, spectroscopic and magnetic properties. [ABSTRACT FROM AUTHOR]

• The flexural stress of WO 3 doped magnets increased by about 59%. • The addition of spherical WO 3 particles improves the remanence and magnetic energy product of 2:17 type SmCo magnets. • The doping of WO 3 particles can induce a high concentration of Cu in the cell boundary phase of 2:17 type SmCo magnet. The influence of spherical WO 3 particles doping on the flexural strength and magnetic properties of Sm(Co bal Fe 0.23 Cu 0.07 Zr 0.02) 7.8 magnets was investigated. As the doping amount increased from 0 wt% to 2.0 wt%, the magnetic properties initially exhibited an increase followed by a decrease, with coercivity increasing from 32.77 kOe to 36.01 kOe and remanence increasing from 11.16 kGs to 11.28 kGs at a doping amount of 0.5 wt%. Moreover, the flexural strength consistently rose from approximately 80 MPa to 127 MPa, representing a significant increase of about 59 %. The presence of WO 3 particles optimizes the magnet's orientation and Cu distribution in the cell boundary phase, thereby enhancing both remanence and coercivity. Additionally, a significant decrease in grain size from 72.04 μm to 33.41 μm was observed, accompanied by a noticeable increase in the content of Sm 2 O 3 phase, which positively contributes to the enhancement of flexural strength. Our research presents a novel technical approach for simultaneously enhancing the magnetic and mechanical properties of 2:17 type SmCo magnets. [ABSTRACT FROM AUTHOR]

• The stability of the alloys is established with the help of structural optimization and computation of cohesive energy. • Electronic properties reveal the half-metallic nature of the alloys. • Alloys also possess the good magnetic moment. • Transport properties suggest that these alloys are suitable candidate for the field of green energy applications. In the quest for new materials, we introduce self-consistent ab initio simulations to investigate the structural and mechanical stability, electronic profile, and transport properties of f -electron-based RaMO 3 (M = Cm, Bk) perovskites by employing density functional theory. The energy optimization indicates that these alloys exhibit stability in the ferromagnetic phase. The examination of mechanical parameters demonstrates the ductile nature of these materials. To elucidate the electronic structure of these alloys, we employed a combination of two approximations: Generalized Gradient Approximation (GGA) and GGA + mBJ. Both approximations confirm the alloys' half-metallic character. The magnetic moments calculated using both approximations were approximately 6 µ B for RaCmO 3 and approximately 7 µ B for RaBkO 3. The thermoelectric performance of these materials is evaluated by investigating different transport parameters such as the Seebeck coefficient, electrical and thermal conductivity and power factor. The comprehensive investigation of these two alloys has the potential to expand their applications in spintronics, thermoelectric devices, and radioisotope thermoelectric generators (RTGs). [ABSTRACT FROM AUTHOR]

• As a result of studies, the methodology for the synthesis of hydrated terbium antimonate has been developed and it has been demonstrated that the phase formation in the fully substituted compound of Tb 0.67 Sb 2 O 6 ∙(3 + n) H 2 O composition occurs after grinding and calcination at 200 °C as a result of ion-exchange reaction. • The Curie-Weiss temperature was determined to be θ CW = − 5 K. • The magnetic ordering temperature has been extrapolated from T P (H) data, as µ 0 H = 0, to be about 0.98 K, where T P is the minimum of temperature dependences dM/dT curve and varies as a linear function of T P = 2.93· H + 0.98. • The values of Δ S and of RC are about 3.8 Jkg−1K−1, 6.2 Jkg−1K− 1 and 18 Jkg−1, 89 Jkg−1 for µ 0 H = 2 T and 7 T, respectively at T = 3 K. In recent years, the idea of using magnetic cooling based on the magnetocaloric effect as an alternative to vapor–gas cooling in liquefaction technology has attracted increasing attention from researchers due to its energy efficiency. The aim of the present research was the synthesis of hydrated terbium antimonate promising for magnetic cooling technology by hydrolysis and mechanochemical activation, and complex analysis of the influence of modifying elements on the physicochemical, magnetic and magneticaloric properties and structure of polyantimonic acid. As a result of studies, the methodology for the synthesis of hydrated terbium antimonate has been developed and it has been demonstrated that the phase formation in the fully substituted compound of Tb 0.67 Sb 2 O 6 ∙(3 + n) H 2 O composition occurs after grinding and calcination at 200 °C as a result of ion-exchange reaction. The Curie-Weiss temperature was determined to be θ CW = − 5 K. The magnetic ordering temperature has been extrapolated from T P (H) data, as µ 0 H = 0, to be about 0.98 K, where T P is the minimum of temperature dependences dM/dT curve and varies as a linear function of T P = 2.93· H + 0.98. The values of Δ S and of RC are about 3.8 Jkg−1K−1, 6.2 Jkg−1K− 1 and 18 Jkg−1, 89 Jkg−1 for µ 0 H = 2 T and 7 T, respectively at T = 3 K. [ABSTRACT FROM AUTHOR]

• A magnetic exchange model was established to understand the physical properties of Fe 5-x GeTe 2. • The critical phenomenon of Fe 4.8 GeTe 2 crystals was systematically investigate in the vicinity of ferromagnetic to paramagnetic phase transition. • The critical exponents and magnetic exchange distance were obtained. • Unraveling the formation mechanism of the complex magnetic state of Fe n GeTe 2. The van der Waals ferromagnet Fe 5-x GeTe 2 has drawn significant interest due to its approximately room-temperature Curie temperature (T C) of 270 to 310 K, which can be regulated through iron deficiency. To comprehend the tunable T C associated with the ferromagnetic exchange mechanism, we systematically investigate the critical phenomenon of Fe 5-x GeTe 2 (Fe 4.8 GeTe 2) crystals around T C. Employing diverse analytical methods for magnetization study, we derived reliable critical exponent values: T C = 285 K, β = 0.364(2), γ = 1.293(1), and δ = 4.62(1). Through a comparative analysis of these critical exponents, the magnetic behavior of Fe 4.8 GeTe 2 is expounded as a three-dimensional (3D) magnetic exchange mechanism, with exchange distance decay modeled as J (r) ≈ r −4.85, closely resembling long-range magnetic coupling in the 3D Heisenberg mode. [ABSTRACT FROM AUTHOR]

• The gallides RE 2 Rh 3 Ga (RE = Gd, Dy, Ho, Er) compounds are fabricated. • The structural, MPT and magnetocaloric properties in RE 2 Rh 3 Ga were studied. • The present RE 2 Rh 3 Ga compound are considerable for cryogenic MR. We herein provide an experimental investigation of the gallides RE 2 Rh 3 Ga (RE = Gd, Dy, Ho, Er) regarding their magnetic properties and magnetocaloric effect (MCE). All of these RE 2 Rh 3 Ga intermetallic compounds crystallized with the Mg 2 Ni 3 Si type structure, space group R– 3 m and are ordered magnetically at low temperatures. Large reversible MCEs around their own ordering temperature were observed in all RE 2 Rh 3 Ga compounds and their magnetocaloric parameters including the maximum magnetic entropy change, refrigerant capacity, and temperature-averaged entropy change are comparable to those of some recently reported candidate materials with prominent performances, making them considerable for cryogenic MR applications. [ABSTRACT FROM AUTHOR]

• Both XRD and Rietveld analysis show single-phase NMCC bulk ferrites. • Surface Morphology study shows intergranular pore size decreased up to y = 0.3. • Optical absorption dominant at visible range as well as band gap enhanced with Mg content. • From the M−H curve experimental and Rietveld µ B show a similar trend distinguished by the canting angle. • T c and the magnetocaloric effect obtained from M−T curve. Bulk ceramics with optimized density are highly prioritized over ferrite nanoparticles to fabricate devices for their optimal magnetic saturation, lower coercivity, and anisotropy, enhanced resistance, etc. To achieve such bulk specimen using Ni 0.5-y Mg y Cu 0.2 Cd 0.3 Fe 2 O 4 disc samples are sintered at 1423 K keeping the heating and cooling rate at 10 K and 5 K respectively. In due course, structural as well as theoretical Rietveld analysis, optical, and magnetic properties have been analyzed using these bulk samples. XRD has explored structural properties and after that these values have analyzed with the Rietveld refinement procedure and obtained goodness of χ2 (1–2) value and other parameters such as lattice parameters, crystal structures, cation distribution, and maximum entropy mapping. Surface morphology and grain size have examined from the as-grown surface without further polishing and annealing by electron microscopy and revealed a decreasing trend of grain size 6.1 µm to 4.2 µm. UV–Vis spectroscopy characterization ensured optical properties for bulk as well as nanopowders and the band gap has been found in the range of 1.4 to 1.6 eV and is increasing with Mg content. Magnetic hysteresis loop exhibits a less decreasing nature up to y = 0.3 of magnetic saturation along with the Law of Approach to saturation which compiles magnetic anisotropy. The temperature-dependent magnetization curves exhibit a sharp decreasing value (i.e. dM/dT maximum) at Curie point, decreasing from 630 K to 505 K with increasing Mg content. At. 3 T magnetic field the changes in relative cooling power value have been found in the range 53.82 J k g - 1 to 37.79 J k g - 1 which could be considered as potential for magnetocaloric refrigeration. [ABSTRACT FROM AUTHOR]

• 3d/4d transition metal ion based Sr 2 MnRuO 6 is prepared using solid state method. • Optical absorption with band gap (3 eV) makes it a potential optical material. • Spin glass kind of magnetic behaviour is observed at low temperature. • Specific heat measurements showed no long-range ordering due to disorderness. Investigation of physical properties in double perovskites, A 2 B′B″O 6 , containing 3d/4d transition metal ions at the B sites is an interesting avenue of research. In this study, we focus on Sr 2 MnRuO 6 , exploring its structural, morphological, optical and magnetic properties. Sr 2 MnRuO 6 was synthesized in single phase using solid-state reaction route. It crystallizes in a tetragonal structure (space group I4/mcm , #140) with lattice parameters a = 5.4633 (2) Å, c = 7.9419 (1) Å. X-ray diffraction analysis revealed no super lattice reflections, indicating disorder in the B-site cations.The Jahn-Teller distortion in Mn-O 6 octahedra,as revealed by XRD results, indicates a high spin state for the Mn3+ ion. The stoichiometric ratio of Sr: Mn: Ru (∼2:1:1), as determined by bond valence sum calculations and confirmed by energy dispersive x-ray spectroscopy agree well with the nominal composition of Sr 2 MnRuO 6. Diffuse reflectance spectroscopy showed strong absorption throughout the visible region with a direct band gap of ∼3 eV, indicating Sr 2 MnRuO 6 is a potential candidate for optical applications. Huge photoluminescence emission observed in the visible region is attributed to Mn3+ ions. The temperature dependence of molar susceptibility data indicates a paramagnetic to antiferromagnetic transition around 195 K. The possible super exchange paths for antiferromagnetic interaction are Ru5+- 4d3 (t 2g 3e g 0) − O1 − Ru5+- 4d3 (t 2g 3e g 0) along the z axis, or Ru5+- 4d3 (t 2g 3e g 0) − O2 − Ru5+- 4d3 (t 2g 3e g 0) in the xy -plane, with the angles between these orbitals being nearly 180°. At low temperatures under a 10,000 Oe field, spin glass type magnetic behaviour is observed. The effective magnetic moment (6.17 μ B) obtained from the Curie-Weiss fit from 260 K to 290 K nearly matched with the theoretical resultant effective moment (6.24 μ B) by considering Mn3+ ions in HS state and Ru5+ ions.Specific heat measurements revealed no long-range magnetic ordering down to 2 K, further suggesting the role of cationic disorder in the magnetic behaviour of Sr 2 MnRuO 6. [ABSTRACT FROM AUTHOR]

• Regulating the stoichiometric ratio in chemistry can reduce T tr , with little effect on T c. • A structural and magnetic phase diagram of Mn 1- x CoGe alloys was proposed. • Stoichiometric control can cause magnetic structure coupling and lead to a giant magnetocaloric effect. • A magnetic entropy change of 27.6 J kg−1K−1 and a cooling capacity of 212.1 J kg−1 were obtained under magnetic field of 5 T. As a family of rare-earth-free magnetocaloric materials, MnCoGe-based alloys have attracted intensive attention in the past few years. In this study, we reveal that the deficiency of either Mn or Co reduces the valence electron concentration of MnCoGe system, thereby lowering its structural transition temperature (T tr) by pushing the Fermi level away from the Mn-Mn antibonding electronic states. Moreover, T tr is found to be more sensitive to Co content. By systematically analyzing the temperature dependent magnetization plots and Arrott curves, it is proven that the magnetic and structural degrees of freedom are coupled in the Mn 0.97 CoGe alloy, resulting in a first-order magnetic phase transition. On the contrary, MnCo 0.98 Ge undergoes a second-order transition. As a consequence, the Mn 0.97 CoGe alloy exhibits a maximum magnetic entropy change of 27.6 J kg−1K−1 under a magnetic field of 5 T near the Curie temperature of 265 K, corresponding to a refrigeration capacity of 212.1 J kg−1. Our work demonstrates Mn/Co vacant MnCoGe alloy as a robust candidate of magnetic substance for room temperature magnetocaloric refrigeration. [ABSTRACT FROM AUTHOR]

Materials exhibiting intriguing magnetic properties, like field-cooled [FC] and zero-field-cooled [ZFC] exchange bias (EB) and negative magnetization (NM), are promising for multiple spintronic applications and also important for basic research to elucidate the underlying driving mechanism(s). While FC-EB is relatively more prevalent among materials possessing mixed-phase magnetism, the technologically more promising ZFC-EB is particularly rare. This makes a recent study of ZFC-EB and NM in SmCrO 3 , a multifunctional orthorhombic rare-earth chromate (R CrO 3), particularly significant. The role of an intrinsic antiferromagnetic coupling between the Sm and Cr magnetic sublattices, present in all R CrO 3 compounds with magnetic R ions, has been suggested to become important to their intriguing functional properties. Recently, NM without EB effect was observed in DyCrO 3 , which contains magnetic Dy 3 + ions. Using detailed characterizations incorporating several control systems, we investigated the origin of these intriguing magnetic properties in SmCrO 3 and DyCrO 3. An emergent magnetically-hard anisotropic phase below the spin-reorientation transition causes a minor-loop effect for the magnetization vs. applied magnetic-field loops, which is found to be entirely responsible for the observed apparent FC-EB and ZFC-EB effects in SmCrO 3. The sign of the ZFC-EB in SmCrO 3 is found to directly correspond to the sign of the trapped magnetic field. Investigation of trapped magnetic fields and precise control over their sign, which are attainable through certain optimized pre-measurement field-ramping protocols, are found critical to identifying intrinsic ZFC-EB and NM effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • All the samples showed single phase. • Decrease in magnetization with substitution Ag+ and Sm3+ can be attributed to anti-site defect. • The Curie temperature of Ag and Sm doped samples was increased and decreased compared to the parent sample, respectively. • The wide temperature range of the −Δ S M near T C by doping. The impact of Sm3+ and Ag+ doping at the Ba2+ site on the structural, magnetic, and magnetocaloric properties of Ba 2 FeMoO 6 (BFMO) double perovskite was compared. Samples were synthesized using the sol–gel method. Rietveld refinement patterns of samples Ba 2-x A x FeMoO 6 (A=Sm, Ag, x = 0.0, 0.025) showed all samples had cubic structures with Fm-3 m space group and no impurity. The lattice parameters and unit cell of the Ba 1.975 Sm 0. 025 FeMoO 6 (BSFMO), and Ba 1.975 Ag 0. 025 FeMoO 6 (BAFMO) samples decreased compared to the parent sample. X-ray photoelectron spectroscopy confirmed that Fe and Mo ions were mixed valence for all samples. The results of magnetization versus temperature (M−T) showed an increase for BSFMO and a decrease for BAFMO samples under an external magnetic field of 0.05 T. The magnetic study indicated a decrease in the transition temperature for BSFMO (∼303 K) and an increase for BAFMO (∼321 K) to compare with the parent sample (∼310 K). The maximum value of magnetic entropy changes ( Δ S M max ) of the BFMO, BSFMO, and BAFMO samples at H=3 T obtained 0.92 Jkg-1K−1, 0.75 Jkg-1K−1, and 0.39 Jkg-1K−1, respectively, and the second-order magnetic phase occurred around the transition temperature. For BFMO, BSFMO, and BAFMO, the relative cooling power (RCP) is 34.48 J/kg, 32.25 J/kg, and 21.97 J/kg, respectively. The second-order magnetic phase transition occurred around the transition temperature for all samples using the energy criterion as well as the universal curve method. In addition, we used Widom's law to determine the critical exponent of the samples, which provides a new thermodynamic method to determine the magnetic phase transition. The results of the magnetocaloric effect indicate that although the maximum entropy changes and relative cooling decrease with doping Ag and Sm ions, they have a wide temperature range of magnetic entropy changes compared to the pristine sample, which can be candidates for magnetic cooling. [ABSTRACT FROM AUTHOR]

Rhenium-based double perovskite oxides (DPOs) are a particularly fascinating class of materials because of high carrier spin polarization, large magnetic anisotropy energy (MAE), and complex electrical behavior along with high Curie temperature (T C). Herein, we discussed the impact of biaxial ([110]) strain ranging from − 5% to ＋ 5% along the a b -plane on the electronic and magnetic properties of CaCuFeReO 6 (CCFRO) DPO using a b - i n i t o calculations. The unstrained system exhibits a ferrimagnetic (FiM) spin ordering as an energetically stable magnetic ground state due to electron hopping between Fe + 3 /Re + 5 t 2 g and Cu + 2 e g orbitals along with a metallic electronic state. Moreover, [010] (b -axis) is the magnetic easy axis that produces the MAE of 5.36 meV, giving a giant MAE constant of 1.97 × 1 0 7 erg/cm 3. The evaluated partial spin-magnetic moment on the Cu1/Cu2/Fe/Re ion is 0.14/0.44/4.04/ − 0. 64 μ B , where " − " sign on the Re moment means that its spin is antiparallel to the other ions, verifying the FiM ordering in the system. Also, the e g , t 2 g / e g , and t 2 g orbital characteristics of Cu + 2 , Fe + 3 , and Re + 5 ions are visible in the spin-magnetization density iso-surfaces plots, respectively. Using the classical Heisenberg model, the computed T C for the unstrained structure is 576 K, which is quite close to the experimentally reported value of 567 K. In addition, it is shown that the FiM metallic behavior in the motif is robust against biaxial ([110]) strain within the considered range. It has also been revealed that T C increased to 5.73%/3.30% for the considered range of − 5% compressive/＋5% tensile strain due to improved structural distortions. [Display omitted] • A ferrimagnetic (FiM) state is found the energetically stable one. • [010] (b-axis) is the magnetic easy axis having MAE of 5.36 meV, giving a giant MAE constant of 1.97 × 107 erg/cm 3. • T C increased to 5.73%/3.30% for the considered range of −5% compressive/+5% tensile strain. [ABSTRACT FROM AUTHOR]

• Tolerance (t) and octahedral (µ) factors deduce the cubic stability of the perovskite crystal. • Negative formation energy indicates that the system is thermodynamically stable. • Ba 2 CoTaO 6 double perovskite oxide exhibits half-metallic ferromagnetism. • Electronic charge density is discussed. • Electronic, magnetic, elastic, and optical properties were calculated. In this study, the computational functionals GGA and mBj of density functional theory (DFT) were employed to explore the electronic structure of tantalum based double perovskite oxide Ba 2 CoTaO 6. Computed tolerance (t) and octahedral (µ) factors deduce the cubic stability of the perovskite crystal. Negative formation energy indicates that the system is thermodynamically stable. The elastic constants satisfy the conditions for cubic stability and the Pagh's index (B/G) evinces the brittle nature. The band structure and total density of states reveal the half-metallic nature with a 4.7 eV insulator indirect energy band gap at the Fermi level in the spin up direction. An integer-valued (4µ B) magnetic moment is observed to favor the half-metallic ferromagnetism in the double perovskite oxide Ba 2 CoTaO 6. Optical properties play a significant role in the design and functionality of optical devices and systems. In this aspect, the two parts of the dielectric function (real and imaginary) and the related parameters have been explored. The observed properties provide insights into possible applications of this system in spintronics and optoelectronics. [ABSTRACT FROM AUTHOR]

The Fe-6.5wt.%Si alloy exhibits remarkable soft magnetic characteristics, such as high magnetic permeability, low coercivity, high resistivity, and nearly zero magnetostriction. These attributes establish it as an ideal material for low-power, low-noise electric motors and transformers. This investigation aimed to assess the impact of annealing temperature (ranging from 800 to 1200 °C for 1 h) on the microstructure, texture, and magnetic properties of a 0.15 mm thick Fe-6.5wt.%Si alloy sheet, which was obtained by subjecting the strips produced through the top side-pouring twin-roll casting (TSTRC) process to multi-pass warm rolling in the temperature range of 600 ∼ 800 °C, avoiding hot rolling. Additionally, the recrystallization mechanism of the annealed sheet at 1100 °C for 1 h was explored. The findings indicate that enhancing the annealing temperature corresponded to a reduction in magnetic induction (B 8 and B 50) as well as iron losses (P 10/50 , P 10/400 , and P 2/1000). The annealed sheet at 1200 °C for 1 h demonstrated the most favorable magnetic properties, displaying iron losses of 0.486 W/kg, 6.895 W/kg, and 1.232 W/kg for P 10/50 , P 10/400 , and P 2/1000 , respectively. These results illustrate excellent overall magnetic characteristics. The coercivity (Hc) of both B 8 and B 50 decreased as the annealing temperature increased in the hysteresis loop measurements. Specifically, for B 8 , it decreased from 62.84 A/m to 24.50 A/m, and for B 50 , it decreased from 78.10 A/m to 35.50 A/m. The average grain size of the samples gradually increased as the annealing temperature ranged from 800 to 1200 °C. The dominant texture observed was {1 1 1}, and the volume fraction of {1 1 1} texture increased while the volume fractions of {1 0 0} and {1 1 0} textures decreased. Upon annealing at 1100 °C for 8 s, the elongated and flattened deformed structures were mainly replaced by equiaxed grains, indicating the completion of the recrystallization process. However, there was a noticeable distinction in the coarsening degree of equiaxed grains based on their orientations. The presence of λ-oriented grains was less prominent, while α-oriented and γ-oriented grains were relatively more abundant. As the annealing time increased from 8 s to 1 h, there was a decrease in the presence of λ-oriented and α-oriented grains, while the presence of γ-oriented grains significantly increased. [ABSTRACT FROM AUTHOR]

• FeCoNiCu 0.5 Si x HEAFs with FCC structure are prepared by magnetron co-sputtering. • Addition of Si reduces the H C and increases the resistivity of HEAFs. • FeCoNiCu 0.5 Si 0.2 HEAFs exhibit good balance of magnetic and electrical performances. • Deposition at moderate high substrate temperatures increase the M S of HEAFs while keeping low H C. It has been known that Si has the effect to increase the resistivity, permeability, and to decrease the magnetostriction coefficient in Si-containing steel as soft magnetic material. On the other hand, high-entropy alloys are intensively studied as soft magnetic materials in recent years, especially as thin films. In the present work, Si-containing (FeCoNiCu 0.5 Si x) high entropy alloy films (HEAFs) have been prepared by magnetron co-sputtering under different deposition conditions. The microstructure and magnetic properties of FeCoNiCu 0.5 Si x HEAFs have been investigated to clarify the effects of Si concentration on microstructure formation and magnetic properties. It has been found that Si addition strongly affects the magnetic properties of FeCoNiCu 0.5 Si x HEAFs of FCC phase by decreasing the coercivity of the films, but hardly affects the phase formation in the films. On the other hand, it has been found that deposition of the films at moderate high substrate temperatures greatly improve the magnetic properties by increasing the saturation magnetization while keeping low coercivity. [ABSTRACT FROM AUTHOR]

We show by extensive Monte Carlo simulations that we need a multi-spin interaction in addition to pairwise interactions in order to reproduce the temperature dependence of the experimental magnetization observed in the perovskite compound Pr 0.67 Sr 0.33 MnO 3. The multi-spin interaction is introduced in the Hamiltonian as follows: each spin interacts simultaneously with its four nearest-neighbors. It does not have the reversal invariance as in a pairwise interaction where reversing the directions of two spins leaves the interaction energy invariant. As a consequence, it competes with the pairwise interactions between magnetic ions. The multi-spin interaction allows the sample magnetization M to increase, to decrease or to have a plateau with increasing T. In this paper we show that M increases with increasing T before making a vertical fall at the transition temperature T C , in contrast to the usual decrease of M with increasing T in most of magnetic systems. This result is in an excellent agreement with the experimental data observed in Pr 0.67 Sr 0.33 MnO 3. Furthermore, we show by the energy histogram taken at T C that the transition is clearly of first order. We also calculate the magnetic entropy change | Δ S m | and the Relative Cooling Power (RCP) by using the set of curves of M obtained under an applied magnetic field H varying from 0 to 5 T across the transition temperature region. We obtain a good agreement with experiments on | Δ S m | and the values of RCP. This perovskite compound has a good potential in refrigeration application due to its high RCP. • Modeling using a multi-spin Interaction for Pr 0.67 Sr 0.33 MnO 3. • Unusual temperature dependence of the magnetization. • First-order phase transition using Monte Carlo energy histogram technique. • Large magnetic entropy change and high RCP. • Good agreement between modeling and experiments on above-mentioned properties. [ABSTRACT FROM AUTHOR]

• A single phase of Ho 4 Co 3-x Cu x was synthesized successfully and the magnetism in the compounds was studied in detail. • The Cu substitution of Co increases the stability of Ho 4 Co 3 phase formation and enhance the MCE in the Ho 4 Co 3-x Cu x compounds. • The Ho 4 Co 3-x Cu x compounds are potential materials for low refrigeration. The phase constitution, magnetic ordering, magnetic phase transition and magnetocaloric properties of the Ho 4 Co 3- x Cu x (x = 0, 0.07, 0.14 and 0.28) samples were investigated in detail. When the content of Cu is 0 and 0.07, the samples are composed of three phases, while a single Ho 4 Co 3 phase is obtained when the Cu content reaches 0.14. The stability of the formation of the Ho 4 Co 3 phase increased with increasing concentration of Cu. For the Ho 4 Co 2.86 Cu 0.14 and Ho 4 Co 2.72 Cu 0.28 compounds, it exhibits a ferromagnetic ordering around the Curie temperature 48 K. The isothermal entropy change (−Δ S M) was calculated based on isothermal magnetization measurements using Maxwell's relation. For an applied magnetic field change of 0–5 T, the maximum magnetic entropy change values were determined to be 11.8 J kg−1 K−1 for x = 0, 14.8 J kg−1 K−1 for x = 0.14 and 18.6 J kg−1 K−1 for x = 0.28, respectively, with the corresponding refrigerant capacity (RC) values of 576 J kg−1, 465 J kg−1, and 503 J kg−1. The considerable magnetocaloric effect indicated that a range of Ho 4 Co 3- x Cu x alloys could be considered potential candidates for low-temperature magnetic refrigeration materials. [ABSTRACT FROM AUTHOR]

• Magnetic and electronic properties of Ho 6 Fe 23−x Co x (x = 0, 1, 2, 3) compounds were investigated for the first time by experimental measurements on their polycrystalline samples combining with first-principles calculation. • The XRD analysis and Rietveld refinement results show that Ho 6 Fe 23−x Co x crystallize in a face-centered cubic Th 6 Mn 23 -type structure with space group Fm 3 ¯ m (No.225), and their lattice parameters decrease with the increasing Co content. • The magnetic entropy change (- Δ S M) for the x = 0, 1, 2, 3 compounds under the applied magnetic field of 1.5 T are 0.594, 1.023, 0.726 and 0.48 J kg−1 K−1 around Curie point, respectively. • The band structures and density of states indicate that Ho 6 Fe 23−x Co x is a good conductor. Magnetic and electronic properties of Ho 6 Fe 23−x Co x (x = 0, 1, 2, 3) compounds were investigated for the first time by experimental measurements on their polycrystalline samples combining with first-principles calculation. The samples of Ho 6 Fe 23−x Co x were successful prepared by a vacuum arc furnace. The XRD analysis and Rietveld refinement results show that Ho 6 Fe 23−x Co x crystallize in a face-centered cubic Th 6 Mn 23 -type structure with space group Fm 3 ¯ m (No.225), and their lattice parameters decrease with the increasing Co content. The M−T curves indicates that AFM-FM transition occurred at Neél temperature T N , the FM-PM transition occurred at Currie temperature T C for Ho 6 Fe 23−x Co x and the FM-PM transition belongs to a second-order transition. The Currie temperature and magnetic compensation temperature for all the samples increases with the increase of the content of Co. The maximum magnetic entropy change (- Δ S M) for the Ho 6 Fe 23−x Co x compounds under an applied magnetic field of 15 k Oe are 0.594, 1.023, 0.726 and 0.48 J kg−1 K−1 around their Currie temperature (T C = 542, 580, 622 and 654 K), respectively. This relatively large - Δ S M of Ho 6 Fe 23−x Co x occurred in a relatively high temperature region and under low applied magnetic field, pointing to the potential application as magnetic refrigeration materials using at higher temperature. The experimental results show that Co doping can regulate the magneto-thermal properties of the materials, so as to improve the magnetic entropy change of the existing magnetic refrigeration materials. The electronic properties of Ho 6 Fe 23−x Co x was studied by using the first-principle calculation. The band structures and density of states indicate that Ho 6 Fe 23−x Co x are good conductor. [ABSTRACT FROM AUTHOR]

• GLNSYMnO 3 has a single-phase orthorhombic perovskite structure sintered at 1250 °C. • The high configurational entropy drives the structural stability of GLNSYMnO 3 even at temperatures below T C. • GLNSYMnO 3 has good magnetism due to the lattice distortion and double-exchange. • GLNSYMnO 3 is a second-order magnetic phase transition material with potential applications in magnetic storage. Rare-earth transition element high-entropy perovskite ceramics (HEPCs) (Gd 0.2 La 0.2 Nd 0.2 Sm 0.2 Y 0.2)MnO 3 (GLNSYMnO 3) were prepared by using a solid-state reaction method, and the structure, morphology and magnetic properties of the GLNSYMnO 3 were studied. The crystalline structure of GLNSYMnO 3 is a smooth surface and similar to "cashews" tubular particles, and a single-phase orthorhombic (Pbnm Space group) perovskite without impurities is confirmed when the sintered temperature reaches or exceeds 1250 °C by the analysis of phase composition and microstructures. Magnetic measurements indicate that GLNSYMnO 3 HEPCs have low Curie temperature (T C = 61 K), but they exhibit a good magnetism by comparison with other high-entropy ceramics, which is caused by the lattice distortion and exchange interactions between high concentrations of Mn3+ (92.4 %) and non-magnetic oxygen ions, promoting the movement of circulating electrons. GLNSYMnO 3 HEPCs did not undergo a phase transition below T C due to high configurational entropy driving structural stability. In addition, GLNSYMnO 3 HEPCs undergo a second-order magnetic phase transition from isothermal magnetization curves and Arrot curves, which have potential applications in magnetic storage. [ABSTRACT FROM AUTHOR]

We investigate the magnetocaloric effect obtained by the rotation of a magnetic field applied to an exchange-coupled multilayer system composed of two different ferromagnetic (FM) materials. We specifically consider a system in which the two FMs have perpendicular uniaxial anisotropy axes and utilize conditions which yield a reorientation of the total magnetization when compensation between the anisotropies of the two layers occurs. We calculate the consequent entropy change associated with the "artificial" reorientation. By using known parameters from MnBi and Co we predict an entropy change of Δ s = 0. 34 J kg−1 K−1 for perfect coupling. Lastly, we study the behavior of the multilayer under a rotating magnetic field via a micromagnetic model. When the layer thicknesses are of the order of the local domain wall width, the magnetic field-induced entropy change can be obtained with magnetic fields one order of magnitude lower than in the uncoupled case. • We investigate the rotational magnetocaloric effect (MCE) obtained in an exchange-coupled multilayer system. • The system has two ferromagnetic materials with mutually perpendicular uniaxial anisotropy axes. • The available MCE is highly dependent on the layer thickness and can reach Δ s/ μ 0 Δ H ∼ 10 J kg−1 K−1 T−1. • Layered materials with optimized anisotropy constants should yield yet higher MCEs. [ABSTRACT FROM AUTHOR]

• Ga-doped Mn 4 N epitaxial films were grown on SrTiO 3 (0 0 1). • A sign reversal of the anomalous Hall resistivity appeared between x = 0.1 and 0.3. • A sign reversal was also observed in the x-ray magnetic circular dichroism between x = 0.1 and 0.3. • The magnetic moment of Mn(II) sublattice was aligned parallel to that of Mn(I) sublattice at x = 0.3. Researchers have focused on anti-perovskite Mn 4 N-based ferrimagnets as potential candidates for spintronic applications since these films have a small magnetization and exhibit perpendicular magnetic anisotropy. Magnetic compensation (or angular momentum compensation) in impurity-doped Mn 4 N at room temperature has attracted particular attention because the magnetization switching can be facilitated in the vicinity of such compensation compositions. In this study, we grew Mn 4− x Ga x N (x = 0.0–1.9) epitaxial thin films on SrTiO 3 (0 0 1) substrates by molecular beam epitaxy and evaluated their crystallinity and surface conditions. The magnetic properties of the grown films were also examined and a sign reversal of anomalous Hall resistivity and hysteresis loops was observed between x = 0.1 and 0.3 at room temperature by magneto-optical Kerr effect microscopy. X-ray magnetic circular dichroism measurement revealed that the magnetic moment of face-centered Mn at x = 0.3 was reversed to be parallel to that of Mn at corner sites, suggesting that the ferrimagnetic-ferromagnetic phase transition occurred with nonmagnetic Ga doping. [ABSTRACT FROM AUTHOR]

• Weak magnetic element V doping with mixed valence states of V2+ and V4+. • Super-Invar behavior with α l = 4.4 × 10-7 K-1 in the x = 0.2 component. • The long-term debates on the different determinations for first-order or second-order transition in TbCo 2 should come from the crystal defects and inhomogeneous polycrystalline distribution on the microscopic scale in different samples themselves as we compared all other research with current work, which is an inspiring conclusion. • Controllable T C with slightly subtracted magnetic entropy change –Δ S M. In this work, the V-doped effect on the magnetic transition and magnetocaloric properties have been studied systematically for TbCo 2 V x (0 ≤ x ≤ 0.2) series. All samples were characterized by powder X-ray diffraction (XRD) as cubic structures (Fd -3 m) at room temperature. The Curie temperatures T C of TbCo 2 V x decrease monotonically from 234 K (x = 0) to 214 K (x = 0.2) corresponding to a monotonically increasing value of lattice a. The slightly diminished magnetic saturation moment M S from 6.35 μ B /f.u to 6.12 μ B /f.u with the x value increasing indicates weak magnetic doping in this system, which can also be reflected in the slight decrease of the maximum values of magnetic entropy change (-Δ S M) from 6.23 J kg-1K−1 to 5.27 J kg-1K−1 (0–5 T). X-ray photoelectron spectrum (XPS) measurements confirm that the weak magnetic doping originates from the multivalences of V2+ and V4+, compared with other normally nonmagnetic V-doped cases reported before. Both the Banerjee criteria and rescaled magnetic entropy change lines deny the first-order transition in parent compound TbCo 2 as reported recently. Almost zero thermal expansion near T C in TbCo 2 with thermal expansion coefficient α l = -1.43 × 10-6 K−1 indicates weak magnetostriction, which is another experimental hint for second-order transition. The deviation of the critical exponents to Mean-field theory in TbCo 2 implies some crystal defects and inhomogeneous polycrystalline distribution inside, which should also be a key point for the divergence of first-order and second-order transition in different samples of TbCo 2 as reported before. Super-invar behavior with α l = 4.4 × 10-7 K−1 was found in the x = 0.2 component by macro-thermal expansion measurement. [ABSTRACT FROM AUTHOR]

• The plates can remain mechanically intact hydrogenated under appropriate pressure. • The magnetocaloric effects of the plates influenced by the hydrogenation time. • La-Fe-Si-H plates with large ΔS m and good mechanical properties were demonstrated. The fabrication of La(Fe, Si) 13 H y plates is very challenging owing to the poor mechanical stability. In this work, La(Fe, Si) 13 plates synthesized by hot-pressing remain mechanically robust after optimizing the hydrogenation process. The hydrogenation behavior was investigated through characterizing the phase structures and magnetocaloric effects of La 0.8 Ce 0.2 Fe 11.51 Mn 0.19 Si 1.3 hydride plates. The saturated hydrogenation plates exhibit the large magnetic entropy change (12.98 J/kg·K), excellent mechanical properties (bending strength ∼ 213 MPa) and good stability under the conditions of the hydrogenating temperature of 593 K, the pressure of 0.13 MPa for 210 min. [ABSTRACT FROM AUTHOR]

• fcc-Cubic structure (space group: Fm-3m) of Fe 50 Ni 50 obtained by ball milling method, followed by annealing quenching. • Magnetization results divulge the presence of long-range ferromagnetic ordering and obtained T C ∼ 762 K. • Modified Bloch Law confirmed the T3/2 and T2 dependency of saturation Magnetization. • Arrott plots study confirms that the nature of ferromagnetic to paramagnetic phase transition is second-order. • Critical exponents (β, γ, δ) are determined using modified Arrott plot, Kouvel-Fisher, and Critical isothermal methods. • Around T C , MCE has significant value in broad T-range. Characteristics of ΔS M and universal curve reinstate SOPT nature. Herein, we report the structural, magnetic and magnetocaloric properties of Fe 50 Ni 50 alloy prepared through the planetary ball-mill. Rietveld analysis of the X-ray profiles confirmed the cubic crystallographic phase with the Fm-3 m space group. The magnetic characterization demonstrates that Fe 50 Ni 50 alloy exhibits the coexistence of magnetic interaction within the ferromagnetic phase with Curie temperature 762 K. The Arrott plot results confirmed the second-order nature of the alloy. Critical exponents were also determined using the modified Arrott plot, Kouvel-Fisher plot and critical isotherm analysis. Obtained results indicated coexisting magnetic behavior, i.e., long-range ferromagnetism and inhomogeneous magnetic state. This alloy also noted a significant magnetocaloric parameters, i.e., magnetic entropy change (−ΔS M ∼ 2.3 J/kg-K) and relative cooling power (RCP ∼ 230 J/kg) at 30 kOe applied field. Both parameters followed power law dependence of magnetic field, and the exponent value supports the ferromagnetic nature along with the coexisting magnetic state. By normalizing the ΔS M curve with rescaled temperature, a universal master curve is also constructed for this alloy, reiterating the second-order nature of the magnetic transition. [ABSTRACT FROM AUTHOR]

• Heusler compounds exhibit a wide range of unique properties. • One of the important applications of some Heusler compounds is as magnetocaloric materials. • To develop promising compounds, the ability to accurately characterize their structure at various scales is critical. • Leveraging various diffraction techniques, enables the understanding of their structure. Heusler compounds are intermetallic alloys that are capable of a wide range of unique properties such as magnetocaloric, thermoelectric, and magnetic-shape-memory effects, antiferromagnetism, superconductivity, and they can even act as topological insulators. These multifunctional behaviors make Heusler alloys prime candidates for numerous smart device applications. However, their specific properties critically depend on their crystalline structures, chemical order, structural phase transformations, and crystallographic texture. Thus, as compositions and processing parameters are varied it becomes essential to be able to accurately characterize the structure of these materials at various scales. This paper provides a brief review of diffraction-based characterization techniques ideally suited for the characterization of Heusler alloys with examples from our previous works including use of synchrotron, neutron, and electron diffraction, especially as a function of temperature and/or magnetic field to explain important phenomena demonstrated by Heusler alloys. [ABSTRACT FROM AUTHOR]

Measurements of magnetization (M) were performed on a series of Er 1 − x Gd x Al 2 (x = 0.1, 0.25, and 0.5) alloys. ErAl 2 and GdAl 2 are ferromagnets with the Curie temperatures (T C) of 14 K and 168 K, respectively. Er 1 − x Gd x Al 2 also showed a ferromagnetic order at T C = 21 K for x = 0.1, 57 K for x = 0.25, and 89 K for x = 0.5. Upon cooling, M (B) curves of Er 1 − x Gd x Al 2 for 0. 1 ≤ x ≤ 0. 5 exhibited a metamagnetic behavior. The field cooled M for Er 1 − x Gd x Al 2 increased below 30 K, indicating a spin-reorientation transition. The magnetic entropy change (Δ S m ) for x = 0. 1 peaked at T C , while a peak or kink was observed for x = 0.25 and 0.5 in Δ S m near 25 K, distinct from a ferromagnetic order. The spin-reorientation due to the Gd substitution is attributed to the magnetic properties and broadened Δ S m (T) curves for Er 1 − x Gd x Al 2 alloys. • Er 1 − x Gd x Al 2 (x = 0.1, 0.25, and 0.5) alloys were synthesized by arc-melting method and were annealed. • Er 1 − x Gd x Al 2 alloys showed ferromagnetic ordering (T C) and spin-reorientation transition (T SR). • Magnetic entropy change for x = 0. 25 and 0.5 exhibited anomalies near T C and T SR • The spin-reorientation transition leads to broadened magnetic entropy change vs temperature plot. [ABSTRACT FROM AUTHOR]

• Magnetic behaivior of the B-doped Mn 60 Ga 20 C 20-x B x system with x = 0, 1, 2, 3, 4 and 5 have been reviled it the temperature imtrval (10–400)K at magnetic field up to 5T. • A ball milling technique followed by pressing the component, and annealing under an ultra-high purity argon atmosphere for 2 h was first time successfully employed to fabricate the samples. • The (x-T C) and (x-M): phase diagrams have been constructed and discussed. • The adiabatic temperature change by direct method revealed a ΔT ad = 0.8 K at T = 250 K for ΔH = 1.8 T for x = 0. We present results on the structural and magnetic properties of the B-doped Mn 60 Ga 20 C 20-x B x system with x = 0, 1, 2, 3, 4 and 5. A ball milling technique followed by pressing the components, and annealing under an ultra-high purity argon atmosphere for 2 h was employed to fabricate the samples. According to the XRD diffraction data, all samples can be described as single-phase compounds (i.e., the Mn 3 Ga cubic phase in the Pm–3 m space group) where impurity phases did not exceed 5 %. The compounds with x < 5 show similar physical behaviors as the parent, Mn 3 Ga 2 C 2 , which can be generally characterized by a low temperature transition from low to high magnetization states. High boron concentrations were found to completely suppress the antiferromagnetic state. The (x-T C) phase diagram at 10 K has been constructed and discussed. The magnetocaloric measurements result in magnetic entropy changes of 3.0 Jkg-1k−1 at 5 T and ΔT ad by direct measurement of about 0.8 K at 1.8 T. [ABSTRACT FROM AUTHOR]

• This work shows that the cooling exponent n decreases with the increment of x. In the range 0.5 < x < 0.75, n has a small dependency on x. But after x > 0.75 it drops down sharply. • Exponent n strongly depends on the magnetic exchange energy ε. In the high x (0.75 < x < 1) valued samples the decrement of the antiferromagnetic interaction is the main reason of the sharp falling of n. • Sample with low value of Curie temperature t C does not follow the relation Δ S P ∝ t C - 2 / 3 , where Δ S P is the peak value of the magnetic entropy change. • The Curie temperature t C linearly decreases with the increment of x. Using Monte Carlo simulation the concentration dependency of the cooling exponent (n) of a binary alloy A x B 1- x mixed spin system (7/2, 3/2) was studied rigorously. For low magnetic field (h) the entropy change (Δ S) , excellently follows the relation Δ S ∝ h n. The exponent n hardly changes with x within the region 0.5 < x < 0.75. But for further increment of x > 0.75, n sharply drops down. The exponent n is strongly affected by the exchange interaction energy (ε). Due to the decrement of the antiferromagnetic interactions n value rapidly decreases. For the increment of x or the number of A(spin-7/2) atom the magnetization M as well as the magnetic entropy change Δ S increases. The phase transition temperature (i.e. Curie temperature) t C linearly decreases for the increase of x. [ABSTRACT FROM AUTHOR]

[Display omitted] • GdNi 4 B, GdNi 4 In, GdCo 4 Al and DyCo 4.6 Si 0.4 prepared via arc-furnace melting/annealing. • GdNi 4 B and GdNi 4 In show dominant ferromagnetic ordering of Gd sublattice. • GdCo 4 Al and DyCo 4.6 Si 0.4 exhibit HT dominant ferromagnetic ordering of Co sublattice. • GdCo 4 Al and DyCo 4.6 Si 0.4 show LT with dominant ordering of rare earth sublattice. • GdNi 4 In exhibits largest magnetocaloric effect from GdNi 4 {B, Al, Ga, Si, In} compounds. The polycrystalline CeCo 4 B-type GdNi 4 B (space group P 6/ mmm , N 191, hP 12), CaCu 5 -type GdCo 4 Al and DyCo 4.6 Si 0.4 (space group P 6/ mmm , N 191, hP 6) and MgCu 4 Sn-type GdNi 4 In (space group F -43 m , N 216, cF 24) were prepared by arc melting with following annealing. The magnetic ordering and magnetocaloric effects of these compounds have been investigated using magnetic measurements in fields up to 90 kOe. GdNi 4 B and GdNi 4 In show dominant ferromagnetic ordering of Gd sublattice with T C of 39 K and 24 K, respectively with magnetic entropy change of −11.3 J/kg·K for GdNi 4 B and −11.8 J/kg·K for GdNi 4 In for a field change of 50 kOe. GdCo 4 Al and DyCo 4.6 Si 0.4 exhibit high-temperature dominant ferromagnetic ordering of Co sublattice with low-temperature spin-reorientation transformation of magnetic ordering and dominant ordering of rare earth sublattice in width temperature interval. In a field change of 50 kOe, the compensation temperature of DyCo 4.6 Si 0.4 is followed via table-like magnetic entropy change of −1.0 J/kg·K at ∼40–240 K, while GdCo 4 Al exhibits magnetic entropy change of around −0.6 J/kg·K at ∼150–300 K. [ABSTRACT FROM AUTHOR]

The Ising model is generalized to two translations on Union Jack lattice with interactions between the spins at the nearest and noncrossing diagonal neighbor sites. Exact analytical expressions are derived for the largest eigenvalue of the Kramers-Wannier transfer matrix as well as for the spontaneous magnetization, taking into account the specified interactions (six parameters of exchange interactions on the whole). The thermodynamic and frustration properties of the model are investigated. The essential features of the behavior of entropy, heat capacity and spontaneous magnetization are revealed. A number of exact expressions for phase-transition temperatures, zero-temperature entropy (residual entropy) and zero-temperature spontaneous magnetization (residual spontaneous magnetization) are obtained. Especially replete with new effects, the model under consideration manifests itself in a wide variety of special cases and relationships with other lattices, including new lattices found and not previously investigated. • Union Jack lattice is generalized to two translations with six exchange interactions. • Analytical expressions for free energy and spontaneous magnetization are derived. • Thermodynamic and frustration properties of the model are thoroughly investigated. • Phase-transition temperatures, residual entropy and magnetization are obtained. • Discovered new lattices open opportunities for obtaining new properties and effects. [ABSTRACT FROM AUTHOR]

• The unit-cell volume expands by 4% during martensitic transformation, which implies a large lattice distortion. • The substitution of Bi for Co atoms in MnCoGe alloy can result in magnetostructural transition.. • Considerable magnetic entropy change and refrigeration capacity were obtained.. • The illustrating structural and magnetic phase diagram of MnCo 1- x Bi x Ge was established. In this work, the substitution of Bi for Co atoms in MnCo 1- x Bi x Ge (x = 0.01, 0.02, 0.04, 0.06, 0.08, 0.1) alloys was prepared. The crystal structure, magnetic properties, and magnetocaloric effect have been analyzed. By tuning the Bi-content in MnCoGe alloys, the reduction of martensitic transformation (MT) temperature and the presence of a first-order magnetostructural transition (MST) were observed. Magnetic field-induced MT indicates that the magnetic field is much harder to drive MT compared to the temperature. With the Bi-content for 0.01 ≤ x ≤ 0.06, orthorhombic-type phase and hexagonal-type phase coexist. Furthermore, we observed an increase in the fraction of the hexagonal-type phase and a corresponding decrease in the fraction of the orthorhombic-type phase. It is beneficial to the refrigeration capacity for the isothermal magnetization curves M(H) on magnetization and demagnetization procedures with small magnetic hysteresis loss. With a magnetic field of 5 T, magnetocaloric effect (MCE) can be observed involving magnetic entropy change (- Δ S M) of 26.42 J kg−1 K−1 for x = 0.06 and refrigeration capacity (RC) of 259.78 J kg−1 for x = 0.01. Thus, this material is considered a fabulous candidate for magnetic refrigeration cooling applications at room temperature. [ABSTRACT FROM AUTHOR]

• Magnetizations are performed on Tb 1.98 Y 1.02 Fe 5 O 12 in strong dc fields up to 200 kOe. • Magnetic transitions between collinear and canted phases are observed near the compensation point T comp = 137 K. • Phases diagrams are mapped out in the H-T plane for H applied along the 〈1 1 1〉, 〈1 1 0〉, and 〈1 0 0〉 axes. • They include second order H C2 lines, one first order I-T comp line, and the critical points C* and I. • The main peculiarities due to the magnetic anisotropy effects are discussed. • The mean field approximation of the two-sublattice model and a high-field method are applied. • Molecular field coefficients of the Fe-Tb interaction and within the Tb sublattice are determined. Magnetization investigations have been performed on single crystal of the substituted terbium-yttrium iron garnet, Tb 1.98 Y 1.02 Fe 5 O 12 in strong dc magnetic fields up to 200 kOe applied along the easy 〈1 1 1〉, the intermediate 〈1 1 0〉, and the hard 〈1 0 0〉 axes of magnetization. When the internal magnetic field H is applied along the two difficult directions 〈1 1 0〉 and 〈1 0 0〉, different field-induced phase transitions between the associated collinear and the so-called canted magnetic phases are observed in the isothermal magnetizations M T (H). They are chiefly manifested by a sudden change for a critical field H C2 with a variation in slope in the temperature region within 60 K around the magnetic compensation point, T c omp = 137.0 ± 0.1 K. The magnetic structure becomes collinear for H applied along the 〈1 0 0〉 direction at a first critical field H C1 ≤ 10 kOe after a substantially curved part where the slope varies when H is increased. Isofield magnetizations M Hap (T) are recorded along the 〈1 1 1〉 direction at fixed external field H ap = 20.09, 60.24, and 70.14 kOe while T varies by steps in the range of 119–151 K around T comp. The magnetic transitions between one canted phase and two inverse collinear phases on each side of T comp are observed by magnetization anomalies at a critical temperature T C2 well-defined with a magnetization jump in the curves of the associated derivatives dM Hap (T)/dT. Based on the (H C2 ,T C2)-points, the experimental magnetic phase diagrams (MPDs) are precisely determined in the H-T plane with a more accurate values of the critical point C* (H C * = 188 ± 1.3 kOe; T C * = 152 ± 2 K) above which, ferri-and ferromagnetic collinear phases exist for all the directions. Other particularity of the MPDs, is the first-order phase transition I-T comp line separating two inverse collinear phases along the axis 〈1 1 1〉 with (H I = 20.09 kOe;T I = 136.33 K), being the coordinates of the critical point I, in agreement with the prediction for weakly anisotropic uniaxial ferrimagnets in a low-field parallel to the easy axis. Based on the mean field approximation applied to a two-sublattice model at high temperature, molecular field coefficients of the Fe-Tb interaction and within the Tb sublattice are obtained and compared to those found previously for TbIG. [ABSTRACT FROM AUTHOR]

• Assessing a solar water heater with turbulator in the appearance of magnetic field. • Analyzing impact of Reynolds number, turbulator twist pitch and riser cross section. • Employing ANN and GMDH to simulate the first law and second law performances. • Improving system output using turbulator, magnetic field and circular cross section. The flat-plate solar collector is the most common and widely used model of solar collectors. This model of solar collectors is more popular than other solar collectors due to its easy installation and lower cost. It is possible to further reduce the cost and size of these systems by improving their performance. For this purpose, simultaneous application of external uniform magnetic field (MF), water-Fe 3 O 4 ferrofluid, and twisted tape turbulator along with changing the cross-section of the serpentine absorber tube of a collector is proposed in the present research. The outlet temperature of working fluid, pressure drop of working fluid, the rate of thermal energy transferred to the flowing fluid in the collector along with the entropy production rate in the system due to fluid friction and heat transfer were considered as the performance parameters of the system. The effect of cross-section of absorber tube (circular, square, triangular), Reynolds number (Re = 500, 1000, 1500 and 2000), pitch distance of turbulator (δ = 150 mm, 200 mm and 250 mm), ferrofluid volume fraction (σ = 0, 1 %, 2 % and 4 %) and magnetic field intensity (0, 600, 900 and 1200 Gauss) on these parameters was investigated numerically using the finite volume method. In the investigations conducted in the absence of MF, collectors equipped with circular and triangular absorber tubes showed the best and worst thermal performance, respectively, while the lowest and highest total entropy production rate was associated with collectors equipped with circular and rectangular tubes, respectively. Moreover, the escalation in σ from 0 % to 4 % and under the MF effect showed an increase of 0.14 %, 8.62 %, 0.45 %, and 4.55 % in the outlet temperature, pressure drop, useful heat, and thermal entropy generation rate, respectively. While the frictional entropy generation diminished by 8.73 %. In addition, the intensification of MF intensity from 0 G to 1200 G led to enhance the outlet temperature, useful heat, and pressure drop, by almost 0.0014 %, 3.96 %, and 0.013 %, respectively at three different σ values. While total entropy generation rate reduces by 0.195 % as MF intensity increases from 0 G to 1200G. Meanwhile, the results of neural network modeling were presented as two second-order polynomial functions to predict the total entropy generation rate and useful heat under the MF effects. [ABSTRACT FROM AUTHOR]

[Display omitted] • TbMn 2 Si 2-x Ge x exhibit large entropy change accompanying two successive phase transitions at T C1 and T C2. • Neutron diffraction investigations have established the formation of a Fmc-ii + F(Tb) between T C1 and T C2. • Existence of Fmc-ii + F(Tb) magnetic cell leads to a pronounced anomalies in the heat capacity. • Different responses of T C1 and T C2 to external field related to Fmc-ii + F(Tb) is highly unusual. The lack of magnetic refrigeration (MR) materials with high magnetocaloric effect (MCE) and large relative cooling power (RCP) in the temperature range required for hydrogen liquefaction (20 K–77 K) is a bottleneck for practical applications of MR cooling systems. The present investigation of TbMn 2 Si 2-x Ge x compounds (x = 0.1, 0.2) by variable temperature neutron and synchrotron X-ray diffraction, magnetization and heat capacity measurements, establish that substitution of Si with Ge in TbMn 2 Si 2 leads to a significant enlargement of the unit cell and modification of the magnetic properties. Two consecutive ferromagnetic first-order transitions occur below 77 K with the third transition from paramagnetism to a collinear antiferromagnetic state being determined around 500 K. The resultant plateau-like MCE with large RCP below 77 K in these designed compounds offers scope for application for hydrogen liquefaction. Detailed neutron investigation confirm that four magnetic states exist within the temperature range 5 K to 500 K, with two successive first-order magnetic transitions below 77 K responsible for the large MCE. Our specific heat studies provide evidence of strong contributions from the nuclear specific heat and the corresponding nuclear specific heat coefficients of A = 430 ± 50 mJ mol−1 K and A = 418 ± 60 mJ mol−1 K have been determined for TbMn 2 Si 2-x Ge x with x = 0.1 and x = 0.2, respectively. The overlapping entropy curves near these successive transitions lead to a plateau-like magnetothermal effect as well as a large reversible MCE for both samples (e.g. ΔS M max = 14.0 J/kg K and ΔT max = 7.6 K; RCP = 379 J/kg for TbMn 2 Si 1.9 Ge 0.1 for an applied field of 5 T) indicating that the material can operate over a wide temperature range – particularly for hydrogen liquefaction. [ABSTRACT FROM AUTHOR]

• A multi-component Laves phase compound Gd 0.2 Tb 0.2 Dy 0.2 Ho 0.2 Er 0.2 Ni 2 has been prepared. • The compound Gd 0.2 Tb 0.2 Dy 0.2 Ho 0.2 Er 0.2 Ni 2 orders ferromagnetically at 32 K. • The sample exhibits excellent low temperature magnetocaloric effect. Polycrystalline rare earth intermetallic compound Gd 0.2 Tb 0.2 Dy 0.2 Ho 0.2 Er 0.2 Ni 2 has been synthesized by arc melting and it has MgCu 2 -type cubic crystal structure at 300 K (space group Fd-3m). Magnetization measurement on arc-melted Gd 0.2 Tb 0.2 Dy 0.2 Ho 0.2 Er 0.2 Ni 2 reveals a paramagnetic to ferromagnetic transition at ∼32 K (T C). The T C is close to the average value of the ferromagnetic transition temperatures of the end member GdNi 2 , TbNi 2 , DyNi 2 , HoNi 2 and ErNi 2 compounds. Using the field-dependent magnetization data measured around T C, isothermal magnetic entropy change (ΔS m) has been estimated. A maximum value of Δ S m m a x = −14.3 J kg−1 K−1 is obtained at 27.5 K for 5 T field change. This value is significant when compared to that in the parent RNi 2 (R = Gd, Tb, Dy, Ho and Er) compounds. The multicomponent compound Gd 0.2 Tb 0.2 Dy 0.2 Ho 0.2 Er 0.2 Ni 2 has also been prepared by melt-spinning under inert atmosphere. The melt-spun sample shows granular microstructure with an average grain size of ∼1 µm. It is found that the bulk magnetic properties are almost retained in the melt-spun sample and the magnetocaloric effect is nearly equal to that in arc-melted Gd 0.2 Tb 0.2 Dy 0.2 Ho 0.2 Er 0.2 Ni 2. The relative cooling power is large and is about 568 J kg−1 and 531 J kg−1 for 5 T field change for the arc-melted and melt-spun Gd 0.2 Tb 0.2 Dy 0.2 Ho 0.2 Er 0.2 Ni 2 samples respectively. [ABSTRACT FROM AUTHOR]

We report the detailed study of the magnetocaloric effect (MCE) in a dipolar-Heisenberg magnet LiGdF 4 using magnetization measurements performed on a single crystal sample. Entropy variation on isothermal demagnetization from the magnetic field up to 3 T is determined in the temperature range 2–10 K for two principal directions of the applied field (parallel and perpendicular to the tetragonal c -axis of the crystal). The MCE is found to be highly anisotropic, with the cooling efficiency being up to twice higher at H ∥ c. The results are nicely interpreted in the frame of a conventional molecular field approach taking into account considerable anisotropy of the paramagnetic Curie–Weiss temperature. These results are compared to earlier studies of MCE in powder samples of LiGdF 4 (Numazawa et al., 2006) as well as with analogous data for other well known magnetocaloric materials. Our findings may open new possibilities to enhance the efficiency of magnetic refrigeration in the liquid helium-4 temperature range. • Strongly anisotropic magnetocaloric effect in a dipolar magnet LiGdF 4 is observed. • High-quality single crystals were studied instead of powder samples. • The effect originates from fine balance/frustration of various magnetic interactions. • Nearly ideal paramagnetic behavior combines with high density of magnetic ions. • Broad opportunities for use in magnetic refrigeration in the helium–temperature range. [ABSTRACT FROM AUTHOR]

• Exploring their behavior and the impact on their physical properties has such a significant interest, especially considering their potential applications across various technological sectors. • Our findings reveal that the ECO system has a bandgap of 1.052 eV for the spin down channel, while the spin up channel exhibits band gap of 1.066 eV, while the EFO system exhibits a slightly smaller bandgap of 0.958 eV. • As observed in this study, the role that f orbitals play in the electronic structure of the modeled systems holds significant importance, especially when considering potential applications. For example, in catalytic applications, it has been observed that A-site rare earth (RE) cations do not directly engage in the electrocatalytic process within ABX3 perovskites. However, they can indirectly influence the physiochemical properties of perovskites, including electronic structure and conductivity, which can, in turn, affect electrocatalytic performance. • The bandgap modulation due to the substitution of Co with Fe atoms can be applied to photovoltaic systems, where such behaviors are sought [65]. Finally, the presence of flat bands attributed to the Eu f states suggests the potential use of these systems in the design of thermoelectric materials. The study of the interactions between rare-earth elements and transition metals plays a crucial role in understanding the diverse magnetic states observed in systems with ABO 3 perovskite structure. Exploring their behavior and the impact on their physical properties has such a significant interest, especially considering their potential applications across various technological sectors. In this research, we investigated the structural, electronic, and magnetic properties of three systems EuCoO 3 (ECO), EuFeO 3 (EFO), and EuCo 0.5 Fe 0.5 O 3 (ECFO). We used the density functional theory based on the Hubbard model (DFT + U) approach to accomplish this. Our findings reveal that the ECO system has a bandgap of 1.052 eV for the spin down channel, while the spin up channel exhibits band gap of 1.066 eV, while the EFO system exhibits a slightly smaller bandgap of 0.958 eV. On the other hand, the ECFO system displays a bandgap value of approximately 0.961 eV for the spin-up channel and 1.6 eV for the spin-down channel. Furthermore, we observed an antiferromagnetic behavior in the EFO system, whereas the ECO and ECFO systems exhibit ferromagnetic behavior. These results provide insight into the distinct magnetic properties of these materials and contribute to our understanding of their potential applications as functional devices in various technological fields. [ABSTRACT FROM AUTHOR]

• Ferrimagnetic transition temperature (T c) gets reduced from 555 (x = 0.0) to 545 K (x = 1.0). • Low temperature M−T curves show spin reorientation, magnetic compensation and paraprocess transition (T B). • - Δ S M is enhanced from 3.92 (x = 0.4) to 4.30 (x = 0.8) J / k g K at 5 T magnetic field. • The measured samples exhibit both normal and inverse magneto caloric effect. • Relative cooling power for x = 0.4 and 0.8 sample is 364.6 and 313.0 J / k g , respectively. • Positive slope in Arrott plots indicate second-order phase transition. The D y 1 - x H o x 3 F e 5 O 12 (Ho-DyIG) with x = 0.0 to 1.0 garnet samples are prepared by solid-state reaction route by sintering them at 1200 °C for 24 hours followed by calcination. The samples have simple cubic structure with Ia 3 ¯ d space group. The lattice constant is obtained from the Rietveld refinement technique and is found to be decreased from 12.4181 Å to 12.3858 Å with Ho doping. All the samples exhibit ferrimagnetic behavior below their transition temperature of 555 K (x = 0.0) to 545 K x = 1.0 . This drop in transition temperature is attributed to the dilution of F e a - O - F e d networks. All the samples show magnetic compensation because of the strong anisotropy induced at lower temperatures. In addition, we have also observed spin reorientation in all the samples of Ho-DyIG series. We have performed magnetocaloric measurements for x = 0.4 and 0.8 samples and observed that the magnetic entropy is improved from 3.92 to 4.30 J / k g K when measured at a maximum applied field of 5 T around their respective Belov tranistion temperature i.e. T B. We have seen both normal and inverse magnetocaloric effects in these samples. To test the extent of magnetic refrigeration capacity, we have calculated the Relative Cooling Power, which comes out to be 364.6 J / k g for x = 0.4 and 313.0 J / k g for x = 0.8 samples at 5 T magnetic field. The Arrott plots are also investigated and they have positive slope suggesting the presence of second-order phase transition in our samples. [ABSTRACT FROM AUTHOR]

• The planar flow casting Fe-6.5Si ribbons after heat treatment at 1100 °C exhibited good comprehensive magnetic properties, with a magnetic induction intensity of B 8 = 1.26 T and B 50 = 1.65 T, and iron loss values of P 1/400 = 14.1 W/Kg and P 0.2/5000 = 11.1 W/Kg. • Texture parameter A and dislocation density are the key factors affecting the magnetic induction intensity of Fe-6.5Si ribbons, showing an inverse correlation with the texture parameter and dislocation density. • The iron loss is mainly influenced by the grain size, with an optimal grain size of 10 μm for this planar flow casting Fe-6.5Si ribbons with 35 μm. Fe-6.5 wt.%Si steel is one of the most attractive soft magnetic materials for making iron cores with low noise and low power loss. The planner flow casting method was regarded as a promising method to obtain ultra-thin ribbons of Fe-6.5Si alloy. In this study, Fe-6.5Si ribbons with a thickness of 0.03 mm were prepared by planner flow casting. Samples were heat-treated at various temperatures. It is revealed that the grain size on the wheel surface and free surface gradually increases with increasing annealing temperature. The initial {1 0 0} fiber texture of the wheel and free surfaces is weakened after annealing, transforming to {0 0 1} 〈5 1 0〉 on the wheel surface and to {2 2 9} < 11 2 2 > on the free surface after annealing at 1150 °C for 1 h. The texture parameter and dislocation density are the key factors affecting the magnetic induction intensity, showing an inverse correlation with the texture parameter and dislocation density. Furthermore, the iron loss is mainly influenced by the grain size, with an optimal grain size of 10 μm. Considering the magnetic induction intensity and iron loss, the optimal annealing temperature is determined to be 1100 °C, resulting in a magnetic induction intensity of B 8 = 1.26 T and B 50 = 1.65 T, and iron loss values of P 1/400 = 14.1 W/Kg and P 0.2/5000 = 11.1 W/Kg. [ABSTRACT FROM AUTHOR]

• The RE 2 Ga 2 Mg (RE = Tm, Er, Ho) compounds were fabricated. • The magnetic and magnetocaloric properties were investigated. • Large conventional and inverse magnetocaloric effects were observed. • The Tm 2 Ga 2 Mg is considerable for cryogenic magnetic cooling. The Mo 2 FeB 2 -type compounds RE 2 Ga 2 Mg (RE = Tm, Er, Ho) (space group P 4/ mbm) exhibit a large magnetocaloric (MC) effect which makes them promising for use in cryogenic magnetic cooling applications. They exhibit low temperature metamagnetic nature below their Néel temperatures of 6.8, 11.7 and 18.4 K for Tm 2 Ga 2 Mg, Er 2 Ga 2 Mg and Ho 2 Ga 2 Mg, respectively. The magnetic entropy change, the temperature-averaged entropy change (3 K-lift), and the relative cooling power under a magnetic field change of 0–7 T are 15.6, 15.4 J/kgK and 275.8 J/kg for Tm 2 Ga 2 Mg; 13.2, 13.0 J/kgK and 268.0 J/kg for Er 2 Ga 2 Mg; as well as 9.1, 9.0 J/kgK and 223.0 J/kg for Ho 2 Ga 2 Mg, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • AlCoCrCuFeNi prepared by arc-melting method. • NPD results indicate magnetic moment mainly in BCC subsystem. • BCC phase shows chemical ordering, reducing symmetry to Pm-3 m. • The AlCoCrCuFeNi shows soft magnetic properties. • AlCoCrCuFeNi forms dendritic microstructure with the Cu-rich FCC phase and the Ni-rich BCC phase. We report on the investigation of magnetic and structural properties of AlCoCrCuFeNi, which is known to crystallize in a dual phase solid solution: the face-centred cubic (FCC) or the body-centred cubic (BCC). The results of neutron (NPD) and synchrotron powder diffraction (SXRD) allow to partially resolve magnetic information coming from BCC and FCC phases, which is impossible in the bulk magnetic measurements. Electron diffraction (PED) revealed that AlCoCrCuFeNi forms dendritic microstructure with the Cu-rich FCC phase and the Ni-rich BCC phase. Lattice parameters obtained from PED method are in good agreement with parameters obtained after refinement on the basis of powder X-ray diffraction measurements. The local crystal and electronic structure around Co was studied using Co K X-ray Absorption Spectroscopy (XAS). The magnetic measurements show that AlCoCrCuFeNi reveal a ferromagnetic transition at about 330 K and displays magnetic hysteresis loop at the room temperature. Results from NPD suggest that the magnetic moment is mostly located in the BCC subsystem. The alloy shows soft magnetic properties. Saturated magnetizations (M s), remanence ratio (M r / M s) and coercivity (H c) of the cast are estimated to be 45.10 emu/g, 5.1 % and 56 Oe at 300 K, respectively. Finally, the BCC-FCC phase transformation up to 673 K (400 °C) was investigated using temperature dependent NPD, where a possible second BCC phase was identified. [ABSTRACT FROM AUTHOR]

• The magnetic properties of RE 2 RuIn (RE = Dy, Ho, Er, Tm) were studied. • The magnetic phase transition characters were analyzed. • Large magnetocaloric effects were observed in RE 2 RuIn. • The RE 2 RuIn are considerable for cryogenic magnetic cooling. In this work, we provide an experimental investigation on the magnetic phase transition (MPT) and magnetocaloric (MCE) properties of the RE 2 RuIn (RE = Dy, Ho, Er, Tm) samples with a bcc superstructure. The indides RE 2 RuIn order magnetically at low temperature and exhibit large cryogenic reversible MCEs around their MPT temperatures. The magnetocaloric parameters including the peak value of magnetic entropy change, temperature-averaged entropy changes with 5 K-lift, and refrigerant capacity under magnetic field change of 0–7 T are determined to be 18.6 J/kgK, 18.2 J/kgK, and 372.2 J/kg around 15.6 K for Dy 2 RuIn, to be 22.6 J/kgK, 22.0 J/kgK, and 415.6 J/kg around 3.0 K for Ho 2 RuIn, to be 21.1 J/kgK, 19.8 J/kgK, and 346.3 J/kg around 6.4 K for Er 2 RuIn, to be 21.3 J/kgK, 20.7 J/kgK, and 347.8 J/kg around 3.2 K for Tm 2 RuIn, respectively. [ABSTRACT FROM AUTHOR]

• In this article, the feasibility of obtaining a magneto-structural coupling over a wide working temperature range of about 127 K (from 206.5 K to 333.5 K) with negligible thermal hysteresis in combination with the structural, microstructural, magnetic, and magnetocaloric properties of a 50 % Co-doped (at the Ni site) polycrystalline (Mn 0.6 Fe 0.4) (Ni 0.5 Co 0.5) Si (MFNCS-0.5) magnetic shape memory alloy (MSMA) has been thoroughly investigated. • Along with leaf-like microstructure, at room temperature, the system shows a mixed phase of TiNiSi type low-temperature high-magnetic (ferromagnetic) orthorhombic martensite and Ni 2 In type high-temperature low-magnetic (paramagnetic) hexagonal austenite, with the dominance of the second one. • The merging of heating and cooling iso-field thermo-magnetization (M-T) curves, the presence of negligible thermal hysteresis in the MH curves, universal magnetic entropy curves, a proposed phenomenological model (across the Curie temperature), and the positive slopes of the Arrott plot (Banerjee criterion) show that the first-order structural and magnetic transition are coupled along with a second-order ferromagnetic to paramagnetic (FM → PM) phase transition (SOPT). • By extrapolating the Arrott plot to the H/M = 0 axis the spontaneous magnetization value very close to 0 K, Ms(0), is found to be 71.92 emu/g (∼1.83 µ B /f.u.). The linear dependency of M S 2 T on T2 below SOPT and the RWR (Rhodes–Wolhfarth ratio) = 4.29 > 1 indicate the long-range itinerant ferromagnetism in this alloy. • A giant magnetic entropy change (Δ S m) of 25.77 J kg−1 K−1 and a refrigerant capacity (RC) of 472.83 J kg−1 are obtained at 6 T field. • This observed magnetic refrigerant's key characteristics, including a giant magnetocaloric effect (MCE) near room temperature (RT), negligible thermal hysteresis loss, a wide operating temperature range of 127 K, and the use of cost-effective, non-toxic constituent elements, make it a suitable and very promising member for applications in solid-state refrigeration technology near RT. In this article, the feasibility of obtaining a magneto-structural coupling over a wide working temperature range of about 127 K (from 206.5 K to 333.5 K) with negligible thermal hysteresis in combination with the structural, microstructural, magnetic, and magnetocaloric properties of a 50 % Co-doped (at the Ni site) polycrystalline (Mn 0.6 Fe 0.4) (Ni 0.5 Co 0.5) Si (MFNCS-0.5) magnetic shape memory alloy (MSMA) has been thoroughly investigated. Along with leaf-like microstructure, at room temperature, the system shows a mixed phase of TiNiSi type low-temperature high-magnetic (ferromagnetic) orthorhombic martensite and Ni 2 In type high-temperature low-magnetic (paramagnetic) hexagonal austenite, with the dominance of the second one. To estimate the magnetocaloric effect (MCE) across the phase transition, the isothermal magnetic measurement technique has been employed. The merging of heating and cooling iso-field thermo-magnetization (M-T) curves, the presence of negligible thermal hysteresis in the MH curves, universal magnetic entropy curves, a proposed phenomenological model (across the Curie temperature), and the positive slopes of the Arrott plot (Banerjee criterion) show that the first-order structural and magnetic transition are coupled along with a second-order ferromagnetic to paramagnetic (FM → PM) phase transition (SOPT). By extrapolating the Arrott plot to the H/M = 0 axis the spontaneous magnetization value very close to 0 K, Ms(0), is found to be 71.92 emu/g (∼1.83 µ B /f.u.). The linear dependency of M S 2 T on T2 below SOPT and the RWR (Rhodes–Wolhfarth ratio) = 4.29 > 1 indicate the long-range itinerant ferromagnetism in this alloy. A giant magnetic entropy change (Δ S m) of 25.77 J kg−1 K−1 and a refrigerant capacity (RC) of 472.83 J kg−1 are obtained at 6 T field. This observed magnetic refrigerant's key characteristics, including a giant magnetocaloric effect (MCE) near room temperature (RT), negligible thermal hysteresis loss, a wide operating temperature range of 127 K, and the use of cost-effective, non-toxic constituent elements, make it a suitable and very promising member for applications in solid-state refrigeration technology near RT. [ABSTRACT FROM AUTHOR]

• The magnetic properties and magnetocaloric effect of Gd 3 BSi 2 O 10 are studied. • Gd 3 BSi 2 O 10 compound experiences a second-order magnetic phase transition at test temperatures range. • Due to the high magnetic density and weak magnetic interaction, a large magnetic entropy change is determined. The adiabatic demagnetization refrigeration which is based on the magnetocaloric effect (MCE) of magnetic materials is an effective technology to attain sub-Kelvin temperature. In this paper, we report the magnetocaloric property of Gd-based borosilicate Gd 3 BSi 2 O 10. It experiences a second-order magnetic phase transition at test temperatures range. Owing to the high Gd3+ ion / anion ligand ratio and weak magnetic interaction, Gd 3 BSi 2 O 10 exhibits a large magnetic entropy change of 59.1 J·kg−1·K−1 at 2.6 K for Δ μ 0 H = 7 T, which is comparable to that of the top-ranked refrigerants operating in the cryogenic range. Besides, Gd 3 BSi 2 O 10 compound exhibits considerable relative cooling power of 543.7 J·kg−1 for Δ μ 0 H = 7 T. These properties demonstrate that Gd 3 BSi 2 O 10 is a promising magnetic refrigeration material. [ABSTRACT FROM AUTHOR]

This work presents the remarkable experimental magnetocaloric properties of the perovskites Pr 0.9 Sr 0.1 Mn 0. 9 3 + Mn 0. 1 4 + O 3 , including the magnetic entropy change | Δ S m | and the Relative Cooling Power (RCP). To understand these striking properties, we elaborate in this paper a model and use Monte Carlo (MC) simulations to study it for comparison. For the model, we take into account nearest-neighbor (NN) interactions between magnetic ions Mn 3 + (S = 2) and Mn 4 + (S = 3 / 2) and the interactions between these Mn ions with the magnetic Pr ions. The crystal is a body-centered tetragonal lattice where the corner sites are occupied by Mn ions and the center sites by Pr and Sr ions in their respective concentrations given in the compound formula. We use an Ising-like spin model describing a strong anisotropy on the z axis. We show that pairwise interactions between ions cannot reproduce the large plateau of the magnetization experimentally observed below the phase-transition temperature. By introducing for the first time a many-spin interaction between Mn ions, we obtain an excellent agreement with experiments. Fitting the experimental Curie temperature T C with the MC transition temperature, we estimate the value of the effective exchange interaction in the system. From this value, we estimate various exchange interactions between ions: the dominant one is that between Mn 3 + and Mn 4 + which is at the origin of the ferromagnetic ordering below T C. We also studied the applied-field effect on the magnetization in the region below and above T C. The obtained MC results for | Δ S m | are in agreement with experiments performed for applied fields from 1 to 5 T. MC results of RCP are also shown and compared to experimental ones. Various other physical quantities obtained from MC simulations including internal energy and specific heat, versus temperature are also shown and discussed. • Experiment on the magnetic properties of Pr0.9Sr0.1MnO3 was carried out. • Magnetization plateau below T_C is found. • Magnetic entropy change is measured as a function of magnetic field. • High Relative Cooling Power at the transition is found. • Modeling to interpret experimental data was carried, using Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

In this study, the magnetic properties and the magnetocaloric effect of the spin-3/2 Blume–Capel model were explored through the Mean Field Theory, developed through a variational principle based on the Bogoliubov inequality to derive thermodynamic expressions such as free energy, magnetization and entropy. The analysis focused on magnetization, free energy and phase diagram with the presence of an external field greater than and equal to zero. The magnetocaloric effect was evaluated by observing the magnetic entropy changes due to different variations of the external magnetic field. Results were analyzed for both continuous and first-order phase transitions. To validate the magnetic entropy results, Maxwell's relations were applied in the regions with continuous magnetization variations, and the Clausius–Clapeyron equation was used in the regions with magnetization discontinuity. • Magnetic properties and the MCE of the spin-3/2 Blume-Capel model were explored. • Model developed through the Mean Field Theory using the Bogoliubov inequality. • Expressions such as free energy, magnetization and entropy were obtained. • Analysis focused on magnetization, free energy and phase diagrams with h ≥ 0. • MCE was evaluated by the magnetic entropy changes due to variation of h. • Results were analyzed for both continuous and first-order phase transitions. • Maxwell's relations were applied to regions with continuous magnetization variations. • Clausius–Clapeyron equation was used in the regions with magnetization discontinuity. [ABSTRACT FROM AUTHOR]

• Ambient pressure synthesis of a series of A'A 3 B 4 O 12 quadruple perovskites. • B-site is occupied by nonmagnetic cations in all compositions. • Effect of smaller size B-site cation on T N of A-site ordering with larger A'-cation. • Remarkable suppression of antiferromagnetic state for mixed Cu2+-Mn3+ occupancy in A-site. • Near perpendicular alignment of Cu2+ and Mn3+ spins suppressed A-site ordering. The magnetic state of A-site Cu2+ sublattice is sensitive to the non-magnetic B-site cations in A'A 3 B 4 O 12 as revealed from ferromagnetic CaCu 3 M 4 O 12 (M = Sn and Ge) and antiferromagnetic CaCu 3 Ti 4 O 12. We report the sensitivity of Cu2+ ordering when part of it is substituted by Mn3+ keeping the B-site cations non-magnetic. We observed that mixed occupancy of Cu2+ and Mn3+ in A-site, long-range ordering of Cu2+ is remarkably destabilized in (Ca/La/Y)Cu 3-x Mn x Ti 4-y Al y O 12 (x/y = 0, 0.5 and 1.0). Samples are characterized by powder X-ray diffraction, FE-SEM imaging, EDX analysis, XPS analysis, Raman spectroscopy and magnetization. The antiferromagnetic ordering of CaCu 3 Ti 4 O 12 is drastically suppressed in CaCu 2 MnTi 3 AlO 12. Introduction of Mn3+ in Cu2+ sublattice largely hampers the Cu2+—Cu2+ interaction. This result is in strong contrast to the system with magnetic cations at B-site. This may be attributed to the incoherent interaction between Cu2+ and Mn3+ spins though they occupy the same crystallographic sites. LaCu 3 Ti 3 AlO 12 and La 2/3 Cu 2.5 Mn 0.5 Ti 3.5 Al 0.5 O 12 show rather similar behaviour. LaCu 3 Ti 3 AlO 12 shows prominent difference in magnetization compare to La 2/3 Cu 3 Ti 4 O 12 , whereas YCu 3 Ti 3 AlO 12 does not with respect to Y 2/3 Cu 3 Ti 4 O 12. The differential magnetic behaviour is possibly due to the size difference between La and Y. The ac-susceptibility measurement in LaCu 3 Ti 3 AlO 12 suggests the formation of short-range ordered magnetic clusters above T N in the paramagnetic phase and there is no evidence of spin glass-like behaviour at low temperature. [ABSTRACT FROM AUTHOR]