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We examine structural and magnetic properties of a series of La–Fe–Si alloys in the region of concentrations where they naturally form two-phase LaFeSi–LaFe13−xSix composites with variable content and connectivity of LaFe13−xSix grains distributed within the LaFeSi matrix. Theoretical calculations confirm that the LaFeSi constituent is magnetically and structurally inert below room temperature and at pressures between −10 and 10 GPa. The LaFe13−xSix constituent, on the other hand, is magnetically and structurally active: it exhibits first-order magnetostructural transformations that, in addition to xSi, can be controlled with temperature, magnetic field, and pressure. In composites where the concentration of the inactive constituent is ∼70 wt. % or greater, the standard, single-step, LaFe13−xSix first-order phase transformation proceeds in two steps separated by over 30 K in a zero magnetic field. Increasing the magnetic field recouples the two steps and restores the single-step phase transformation pathway. We analyze the roles of stresses caused by both thermal expansion mismatch and the first-order magnetic phase transition in LaFe13−xSix to rationalize the observed physical behaviors that emerge as the temperature or/and magnetic field vary. [ABSTRACT FROM AUTHOR]

Magnetocaloric materials, which exploit reversible temperature changes induced by magnetic field variations, are promising for advancing energy-efficient cooling technologies. The potential integration of two-dimensional materials into magnetocaloric systems represents an emerging opportunity to enhance the magnetocaloric cooling efficiency. In this study, we use atomistic spin dynamics simulations based on first-principles parameters to systematically evaluate how magnetocaloric properties transition from three-dimensional (3D) to two-dimensional (2D) ferromagnetic materials. We find that 2D features such as reduced Curie temperature, sharper magnetic transition, and higher magnetic susceptibility are beneficial for magnetocaloric applications, while the relatively higher lattice heat capacity in 2D can compromise achievable adiabatic temperature changes. We further propose GdSi 2 as a promising 2D magnetocaloric material. Our calculation predicts that GdSi 2 exhibits an isothermal entropy change Δ S M of 22.5 J kg − 1 K − 1 and an adiabatic temperature change Δ T a d of 6.2 K, near the hydrogen liquefaction temperature (T C ≈ 25 K). Our analysis offers valuable theoretical insights into the magnetocaloric effect in 2D ferromagnets and demonstrates that 2D ferromagnets hold promise for cooling and thermal management applications in compact and miniaturized nanodevices. [ABSTRACT FROM AUTHOR]

In this article, a comprehensive study of the effect of calcium substitution on structural magnetic, magnetocaloric properties, and role of Griffiths phase on magnetocaloric properties of half-doped manganites L a 0.5 S r 0.5 − x C a x Mn O 3 (x = 0 , 0.25 , 0.5) ] have been presented. A structural phase transition I4/mcm − Pbnm is observed in the whole series. The system exhibits two magnetic transitions for Ca-00 and Ca-25, whereas only one phase transition is observed for Ca-50. Paramagnetic (PM)–ferromagnetic (FM) transition is observed in the whole series and ferromagnetic (FM) - antiferromagnetic (AFM) phase transition is only observed in Ca-25. Interestingly, short range FM clusters exist in the PM matrix of Ca-50, which is a signature of Griffiths phase (GP). The confirmation of GP has been carried out by performing iso-field magnetization measurements at 200 Oe, 500 Oe, and 1 kOe, respectively. Further magnetocaloric properties have been discussed on the basis of isothermal magnetization curves recorded at certain temperature intervals. Calcium substitution favors the enhancement of magnetic entropy change in the series, especially for Ca-50, a magnetic entropy change of 4.5 J/(kg K) with relative cooling power of 180 J/kg under 5 T magnetic field was observed. Iso-field magnetization and magnetocaloric effect along with critical behavior analysis have been carried out to probe the GP and other inhomogeneities present in the respective series. [ABSTRACT FROM AUTHOR]

We demonstrate magnetocaloric entropy change and compensation temperatures in ferrimagnetic Gdx(Fe10Co90)100−x amorphous thin films with transition metal-rich and rare earth-rich configurations. Thin films are sputtered with same Gd/FeCo elemental ratio at different thicknesses and of various Gd/FeCo ratios at a constant thickness to understand the effect of these two parameters on an antiferromagnetically coupled magnetic sub-lattice system. Temperature- and field-dependent magnetic measurements [M(H,T)] and magnetocaloric studies are performed over a broad range of temperature (70–600 K) by applying a magnetic field of ±15 kOe on sputter deposited 90 nm thin films of Gdx(Fe10Co90)1−x(x = 30,40,50,55,70). The compensation temperature is found to increase with increasing Gd concentration for thin films of the same thickness. A high magnetocaloric entropy change around 0.97 J/kg K (ΔH = ± 15 kOe) is observed for thin films having the same Gd/FeCo elemental ratio. Furthermore, we observed a "table-like" magnetocaloric entropy change in GdFeCo thin film stacks with a high operational window (60 K) at a low applied field for an Ericsson magnetic regenerator around room temperature. The studies will provide important insight into magnetocaloric studies for Ericsson-cycle refrigeration in thin films having antiferromagnetically coupled sublattices. [ABSTRACT FROM AUTHOR]

The advancement of magnetic materials with coupled magneto-structural phase transition (MST) to fulfill the ultimate objectives of practical solid-state cooling applications requires a better understanding of the hysteresis phenomenon linked across the phase transition region along with the large magnetocaloric parameters. For the present sample Mn0.65Ni0.65Fe0.70Si, the MST is associated with a sharp jump in magnetization along with a small thermal hysteresis of ∼13 K. A giant isothermal magnetic entropy change (| Δ S M max |) of ∼37.6 J kg−1 K−1 at 299 K and effective refrigerant capacity (R C effe ) of ∼214.3 J kg−1 under ΔH = 30 kOe is obtained with excellent compatibility between the martensite and austenite phases. The geometrical compatibility condition, i.e., very small (∼0.55%) deviation of the middle eigenvalue (λ 2) from unity justifies the observation of small hysteresis in the present material. The investigation of hysteresis behavior under different extents of the driving forces (temperature or magnetic field) reveals that both the driving forces trigger equally the phase transition and are responsible equivalently for the hysteresis phenomenon. The present study provides a pathway to understand the complexity of the hysteresis behavior, its impact on the reversibility of magnetocaloric effect, and its minimization by optimizing the geometrical compatibility condition between the austenite and martensite phases. [ABSTRACT FROM AUTHOR]

Ferrimagnetic antiperovskite Mn 4 N has received growing interest due to room-temperature observation of large perpendicular magnetic anisotropy, low saturation magnetization, and ultrafast response to external magnetic fields. Comprehensive understanding of the underlying magnetic structure is instrumental in design and fabrication of computer memory and logic devices. Magneto-optical spectroscopy provides deeper insight into the magnetic and electronic structure than magnetometry. Simulations of a magneto-optical Kerr effect in biaxially strained Mn 4 N are performed using density functional theory and linear response theory. We consider three ferrimagnetic phases, two collinear and one noncollinear, which have been investigated separately by earlier studies. The simulated spectra are compared to measured magneto-optical data available in recent literature. One of the collinear ferrimagnetic phases is found to be consistent with the measured spectra. We show that an admixture of the noncollinear phase, which is the ground state of unstrained Mn 4 N, further improves the agreement with measured spectra, and at the same time, it could explain the lower than predicted net moment and magnetic anisotropy observed in thin films on various substrates. [ABSTRACT FROM AUTHOR]

Magnetocaloric properties of TbCrO3 and TmCrO3 are reported and compared with those of the previously reported rare-earth chromites RCrO3 (R = Gd, Dy, Ho, and Er) and other perovskite-type oxides. The samples of TbCrO3 and TmCrO3 in this work were synthesized using a citrate gel combustion technique, and their magnetic properties were investigated and compared with those reported previously on RCrO3 (R = Gd, Dy, Ho, and Er). The Cr3+–Cr3+ ordering temperatures were found to strongly depend on the ionic radii of the rare-earth. By fitting the dc magnetization data with modified Curie–Weiss law including the Dzyaloshinsky–Moriya antisymmetric exchange interaction (D) and the symmetric exchange constant Je, spin canting angles (α) were obtained. In general, α was found to increase with the decreasing ionic radii of R3+ in RCrO3. The magnetocaloric properties investigated included the magnetic entropy change (−ΔS) for a given change in magnetic field (ΔH), the corresponding adiabatic temperature change (ΔTad), and their relative variations (ΔTad/ΔH) and (−ΔS/ΔH). It is observed that for RCrO3, (−ΔS) measured in the vicinity of the ordering temperature of R3+–R3+, varies almost as G2/3 where G is the de Gennes factor. Among RCrO3, GdCrO3 shows the largest value of (−ΔS/ΔH), because of its largest G factor and its magnitudes of (ΔTad/ΔH) and (−ΔS/ΔH) compare well with the reported values for the perovskites GdFeO3 and EuTiO3. These comparisons presented here provide useful information on the potential use of these materials in magneto-refrigeration technology. [ABSTRACT FROM AUTHOR]

We report a large cryogenic magnetocaloric effect stemming from an unconventional borderline first-order magnetic phase transition with negligibly small thermomagnetic hysteresis in a rare-earth-based intermetallic compound PrNdIn. The sample exhibits maximum magnetic field-induced entropy change as large as −10 J/Kg K (for 20 kOe magnetic field change) near the boiling point of oxygen. Magnetocaloric properties of PrNdIn are comparable to those of other known potential magnetocaloric materials with operating temperatures ranging between 50 and 125 K. The magnetic properties of the present sample are qualitatively reminiscent of those of the binary Pr2In and Nd2In, including the emergence of a second low-temperature anomaly in the temperature dependence of magnetization. [ABSTRACT FROM AUTHOR]

In this work, we applied Monte Carlo simulations under the Metropolis algorithm to study the magnetic and magneto-caloric properties of the fullerene C 3 6 system formed with mixed spins: 2 and 5/2. We inspected the effects of not only the crystal magnetic field but also the external magnetic field and the coupling interaction between spins. In the first part, we illustrated the ground state phase diagrams in the planes of the external magnetic field, the coupling interaction between spins and the crystal magnetic field. Also, we have established these phase diagrams for null temperature. It is found that not only the total magnetizations predict the blocking temperature value t B = 5. 5 1 1 7 , but also the magnetic susceptibilities confirm this value. The effects of varying temperature values when fixing the other physical parameters have been outlined. In particular, the studied system showed a shifting between the phases the ferromagnetic phase and the paramagnetic one, at very low temperature values. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect has been extensively investigated in various types of magnetic solids to not only develop practical magnetic cooling applications but also deepen the understanding of these materials' underlying inherent properties. Through experimental determination and theoretical calculation, we conducted a systematic investigation of Gd 4 Ga 2 O 9 oxide in terms of its structural, magnetic, and magnetocaloric properties and found it to crystallize in a monoclinic structure belonging to the space group P 2 1 / c and to possess an antiferromagnetic semiconducting ground state. The consistent elements were uniformly distributed up to the nanoscale and presented as Gd3+, Ga3+, and O 2 states, respectively. The magnetocaloric performances of Gd 4 Ga 2 O 9 oxide were checked according to the parameters of maximum magnetic entropy change, refrigerant capacity, and temperature-averaged entropy changes (lift of 5 K), which were determined to be 25.77 J/kgK, 218.27 J/kg, and 23.43 J/kgK under 0–7 T magnetic field change. These parameters of Gd 4 Ga 2 O 9 oxide are comparable to those of some recently reported materials with prominent performances, which means that it can be considered for cryogenic magnetic cooling applications. [ABSTRACT FROM AUTHOR]

We herein fabricated two gadolinium-transition metal-based high entropy (HE) oxides of Gd(Mn 0.25 Fe 0.25 Al 0.25 Cr 0.25)O 3 [denoted as Gd(4 TM 0.25)O 3 ] and Gd(Mn 0.2 Fe 0.2 Al 0.2 Co 0.2 Ni 0.2)O 3 [denoted as Gd(5 TM 0.2)O 3 ] and determined their structural, magnetic, and magnetocaloric properties. Both of present HE oxides are found to crystallize in the single-phase perovskite-type orthorhombic structure with a homogeneous microstructure and exhibit prominent cryogenic magnetocaloric performances. The values of magnetic entropy change, refrigerant capacity, and temperature-averaged entropy change (6K-lift) under the magnetic field change of 0–7 T are estimated to be 20.34 J/kgK, 295.4 J/kg, and 19.56 J/kgK for Gd(4 TM 0.25)O 3 , and to be 22.45 J/kgK, 258.2 J/kg, and 20.79 J/kgK for Gd(5 TM 0.2)O 3 , respectively, which are comparable with recently reported candidate materials for practical magnetic cooling. These findings not only indicate potential applications of present perovskite-type Gd(4 TM 0.25)O 3 and Gd(5 TM 0.2)O 3 HE oxides, but also provide meaningful clues for exploring HE oxides with prominent cryogenic magnetocaloric performances. [ABSTRACT FROM AUTHOR]

We study the asymptotic growth of the entanglement entropy of ground states of non-interacting (spinless) fermions in R 3 subject to a constant magnetic field perpendicular to a plane. As for the case with no magnetic field we find, to leading order L 2 ln (L) , a logarithmically enhanced area law of this entropy for a bounded, piecewise Lipschitz region L Λ ⊂ R 3 as the scaling parameter L tends to infinity. This is in contrast to the two-dimensional case since particles can now move freely in the direction of the magnetic field, which causes the extra ln (L) factor. The explicit expression for the coefficient of the leading order contains a surface integral similar to the Widom–Sobolev formula in the non-magnetic case. It differs, however, in the sense that the dependence on the boundary, ∂ Λ , is not solely on its area but on the "surface perpendicular to the direction of the magnetic field". We utilize a two-term asymptotic expansion by Widom (up to an error term of order one) of certain traces of one-dimensional Wiener–Hopf operators with a discontinuous symbol. This leads to an improved error term of the order L 2 of the relevant trace for piecewise C 1 , α smooth surfaces ∂ Λ . [ABSTRACT FROM AUTHOR]

With the growing attention to perovskite materials in the field of magnetic refrigeration. In this work, La0.8−xPrxSr0.2MnO3 (x = 0.05, 0.10, 0.15) (LPSMO) samples were synthesized through the sol–gel method. The effects of Pr3⁺ doping on the structure, morphology, and magnetization of LPSMO were investigated. The XRD analysis revealed that the LPSMO samples have a rhombohedral structure within the R-3c space group. As the amount of Pr3⁺ doping increased, the cell volume decreased. The magnetic properties of LPSMO exhibited a transition from ferromagnetic (FM) to paramagnetic (PM) near the Curie temperature (Tc), with Tc decreasing as the Pr3⁺ doping level increased. The second-order magnetic phase transition of LPSMO near Tc was confirmed by employing the MPMS. The maximum magnetic entropy change ( - Δ S M max ) of LPSMO is 4.92 J/(kg·K) (x = 0.05), 5.13 J/(kg·K) (x = 0.10) and 5.04 J/(kg·K) (x = 0.15) when the external magnetic field (H) = 5 T, separately. Meanwhile, the relative cooling power (RCP) of LPSMO are 283.88, 276.71, and 289.60 J·kg−1, respectively. The experiments indicate that LPSMO has promising application prospects. [ABSTRACT FROM AUTHOR]

Erbium orthophosphate ErPO4 was successfully prepared. The XRD pattern analyses have proved that the ErPO4 crystallizes in the tetragonal structure (I41/amd). Under a magnetic field of 50 kOe, the magnetic entropy change (− ΔSM) reaches 23.78 J/kg K at 2.6 K for ErPO4. The value of the relative cooling power is 475 J/kg. The lowest temperature and the large MCE have inferred that ErPO4 is a potential candidate for sub-kelvin magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

FeRh 0.8 Pd 0.2 is known to exhibit near room-temperature first-order antiferromagnetic (AF)–ferromagnetic (FM) transition, typical of chemically ordered FeRh system. In addition, it is also reported to show martensitic transition at a lower temperature. In this work, the effect of sample history on transition temperature (T t) and the magnetocaloric effect (MCE) have been studied. The experimentally determined MCE parameters across FM to AF transition induced either by isothermal magnetic field sweep or by temperature sweep showed a large isothermal change in entropy around room temperature, i.e., 14 J/kg K for 50 kOe magnetic field change, whereas MCE corresponding to AF–FM transition depends on cooling history. Our study shows that in the presence of martensite phase, the peak value of MCE is shifted to higher temperatures but with significantly reduced magnitude. [ABSTRACT FROM AUTHOR]

We explore the existence of spin glass phase in FeCo/FePt bilayers arising due to disordered ferromagnet. The non-ergodic and highly degenerate landscape of the spin glass phase at low temperature explains the origin of complex magnetic texture in the FeCo/FePt system. Upon cooling the bilayered system, the magnetic texture undergoes spin freezing below 120 K as evident from the bifurcations in zero field cooling and field cooling magnetizations at low magnetic field as a manifestation of broken ergodicity. The uncompensated magnetic moments originating in the spin glass state result in slow time dynamics of thermoremanent magnetization. Consequently, the bilayers demonstrate an intriguing magnetic memory effect in which the magnetic state of the system could be retrieved upon isothermal ageing below 120 K after reversing the temperature cycle. Thermal treatment deteriorates the spin glass behaviour and shows a transition to strong ferromagnetic character in FeCo/FePt bilayers. [ABSTRACT FROM AUTHOR]

The cryogenic magnetocaloric effect has attracted great attention due to its application in cryogenic refrigeration technology, which is essential for space science and quantum computing. In this study, the magnetocaloric effect of Gd2GeMoO8 (GGMO) and Dy2GeMoO8 (DGMO), which were prepared by simple solid-state reactions, had been investigated. The XRD refinement analysis suggested that GGMO and DGMO crystallize in a tetragonal structure. A large magnetic entropy change (ΔSM) of −41.2 J kg−1 K−1 was observed at 1.8 K for GGMO under a magnetic field (ΔH) of 7 T. A moderate ΔSM of −14.1 J kg−1 K−1 was obtained at 4.5 K under a ΔH of 7 T in DGMO. The refrigeration capacity and relative cooling power reached 257.4 and 337.8 J kg−1 for GGMO and 133.3 and 143.7 J kg−1 for DGMO, respectively, under a ΔH of 0–7 T. Our results suggest that GGMO is a competitive cryogenic magnetic refrigeration material. [ABSTRACT FROM AUTHOR]

The electronic and thermoelectric properties of the perovskite LaCoO3 compound were studied using first-principles calculations. However, Monte Carlo calculation (MC) combined with the Metropolis algorithm, calculates the magnetic and magneto-caloric properties. The partial moment of the Cobalt atom (Co) and exchange coupling interactions for Co-d orbital at high spin (HS: S = 2), show values µCo = 2.54 ${\rm \mu }_{B\; \comma }J_1^{{\rm Co}-{\rm Co}} = 2.39\; {\rm meV} \comma \; J_2^{{\rm Co}-{\rm Co}} = 0.9\; {\rm meV}\comma$ μ B , J 1 Co − Co = 2.39 meV , J 2 Co − Co = 0.9 meV , respectively. The calculated Curie temperature value (TC) is 100 K, which agrees with the experimental results, such as the LaCoO3 metallic perovskite has a secondary Ferro-Para magnetic transition around TC. The evolutions in magnetic and magnetocaloric (MEC) properties with external magnetic fields were also studied. Finally, thermoelectric properties are examined. [ABSTRACT FROM AUTHOR]

This research paper focused on investigating the influence of various factors on steady Couette flow beneath a permeable bed. Factors studied included aligned magnetic field, thermal radiation, temperature gradient heat source, viscous dissipation, and Joules dissipation. The momentum and energy equations governing flow and heat transmission were analytically solved to predict the generation of entropy. The findings were visually presented through graphical representations, which effectively demonstrated the effect of these factors on the fluid's velocity, temperature, entropy production, and Bejan number. In addition, the shear stress and rate of heat transfer coefficient at the channel walls were computed and their behavior was documented in tables to provide further insights. [ABSTRACT FROM AUTHOR]

Multicomponent rare earth intermetallic compounds Tb0.33Ho0.33Er0.33Ni and Dy0.33Ho0.33Er0.33Ni crystallize in orthorhombic FeB-type structure (Space group Pnma, No. 62, oP8) and order ferromagnetically at 59 K and 40 K (TC) respectively. Hydrides of these samples show a presence of ~ 10-nm size nanoparticles with unit cell volume expansion. Magnetization measurements reveal that hydrides Tb0.33Ho0.33Er0.33NiH1.9 and Dy0.33Ho0.33Er0.33NiH1.9 remain paramagnetic from 300 K down to 5 K. Magnetization value at 5 K in 70 kOe field is ~ 5.1 µB/f.u. and 5.5 µB/f.u., respectively, for Tb0.33Ho0.33Er0.33NiH1.9 and Dy0.33Ho0.33Er0.33NiH1.9 samples. Despite the lack of ferromagnetic order, hydrides exhibit large low-temperature magnetocaloric effect with maximum isothermal magnetic entropy change values of about − 11.6 Jkg−1 K−1 at 14 K and – 12.9 Jkg−1 K−1 at 8 K respectively for 50 kOe magnetic field change. [ABSTRACT FROM AUTHOR]

The novelty of this paper is examining the impacts of Hall currents on Sisko nanofluid slip flow generated by an exponentially stretching sheet in the existence of entropy generation. Entropy generation assessment, Brownian, thermophoresis and Bejan numbers during convection flow are explored in the presence of the Hall effect. The pertinent parameters are Hall parameter m, a magnetic field parameter M, Brownian motion parameter N b , thermophoresis parameter N t , generalized thermal Biot number γ 1 , generalized velocity slip parameter λ and material parameter of Sisko fluid A. The changes in pertinent parameters on principal and secondary velocities, entropy generation and temperature are discussed. The coefficients of local skin friction, Brownian, thermophoresis and Nusselt/Sherwood numbers are expressed in a tabular structure. Two different kinds of power-law nanofluid, Pseudoplastic (n = 0. 7) and dilatant fluid (n = 1. 5) are considered. The current results exposed that growth in magnetic field parameter diminishes the nanofluid axial velocity and boosts the profiles of temperature, secondary nanofluid velocity and nanoparticle volume fraction. The coefficients of local skin friction are enhanced according to a growth in the magnetic field factor. The Pseudoplastic fluid supports the velocity, temperature and nanoparticle volume fraction profiles compared to the dilatant fluid. The local entropy generation number, Bejan number, local skin friction coefficients and local Nusselt/Sherwood numbers are influenced by the pertinent parameters. [ABSTRACT FROM AUTHOR]

The principal aim of this investigation is to examine the gold and magnesium oxide hybrid nanoparticles in different physical capacities on the water-based hybrid nanofluid and elaborate on an erratic squeezing flow among both infinite plates. Melting effect and thermal radiation depict heat transfer features. Production of the Bejan number and entropy is upward. The explains the governing equations, and the standard transformation is supplied. The numerical solutions are carried out using an efficient finite element method. To analyze difference between heat transfer and its implication in industrial zone, the Nusselt number was arranged in a horizontal pattern. The results showed that a thicker thermal boundary layer increased the Eckert number and the volume fraction of gold nanoparticles. Anyhow, the heat transfer rate by Au–MgO/water was necessarily greater than the Au–water. The obtained results are excellent and vigorously oppose those that are applicable to the literature by the attached position. It was established for hybrid nanofluids to display higher entropy generation rates. The outcomes of this analysis were the consequence of the appraisal of the impact on few required form parameters in heat transfer and consequently on the expansion for industrial use. [ABSTRACT FROM AUTHOR]

In this paper, polycrystalline Lu 1- x Dy x Fe 0.5 Cr 0·5 O 3 (0 ≤ x ≤ 0.15) perovskite ceramics were synthesized via a conventional solid-state-reaction technique. Structural and magnetic properties of the samples were experimentally studied. The cell volume of the lattice expands with the rise in Dy3+ amount. The measuring of magnetic properties shows that the undoped sample exhibits a negative magnetization effect with a compensation temperature of 231.1 K, while the Dy-doped samples display negative magnetization effects between two compensation temperatures. The magnetic switch experiment demonstrates the significant potential for practical applications through stable and repeatable switching of magnetization state by adjusting the external magnetic field between 50 Oe and 300 Oe. Besides, the presence of two compensation temperatures which can be regulated by changing the doping content or external magnetic field provides more possibilities for application. Moreover, based on the comprehensive analysis of the experimental results, it is believed that the negative magnetization effect originates from the competition of magnetic moments in different directions. Meanwhile, the second compensation temperature occurs in low temperature region might be attributed to the additional positive magnetic moment contributed by the paramagnetic Dy3+ ions. [ABSTRACT FROM AUTHOR]

We herein provided a systematical determination of the structural and magnetic properties, especially of the magnetocaloric effect (MCE) and magnetocaloric performances of four rare-earth oxychlorides, i. e., the RE OCl (RE = Ho, Dy, Tb and Gd) compounds. The studied RE OCl compounds are all crystallized in the tetragonal matlockite structure (P 4/ nmm space group) and the RE , O, and Cl elements are with the RE 3+, O2−, and Cl− valence states, respectively. The DyOCl, TbOCl and GdOCl compounds reveal an antiferromagnetic transition at around approximate 9.5, 3.7 and 4.8 K, respectively. The magnetocaloric performances are checked by the maximum magnetic entropy change, relative cooling power, and temperature-averaged entropy change with 5 K lift, which are found to be 14.16 J/kgK, 375.55 J/kg and 13.89 J/kgK for HoOCl, to be 14.88 J/kgK, 488.14 J/kg, and 14.60 J/kgK for DyOCl, to be 14.59 J/kgK, 419.67 J/kg, and 14.42 J/kgK for TbOCl, and to be 16.16 J/kgK, 213.68 J/kg, and 14.39 J/kgK for GdOCl, with the magnetic field change of 0–7 T, respectively. [ABSTRACT FROM AUTHOR]

• A magnetic refrigerant prototype with two magnetic poles was designed. • The system has a high magnetic field utilization rate. • The cooling performance and power consumption were studied. • The maximum temperature span of this system is 17.5 K. • The COP of AMR were calculated and analyzed. Room temperature magnetic refrigeration technology is a potentially efficient and environmentally friendly refrigeration technology. A magnetic refrigeration prototype with two high/low magnetic field regions was designed and built. The device consists of eight beds, using gadolinium particles as the magnetocaloric material, with a total filling mass of 1.35 kg. The hydraulic system consists mainly of a magnetic centrifugal pump, solenoid valves, and check valves. The flow of the heat transfer fluid through the regenerators is controlled by controlling the opening and closing of the solenoid valves. The no-load temperature span, cooling capacity, power consumption, and COP of the regenerators were investigated separately. The maximum no-load temperature span of 17.5 K was obtained at an AMR frequency of 0.5 Hz and flow rate of 1.15 L/min. The total power consumption and the magnetic power and pumping power were analyzed for different operating conditions. [ABSTRACT FROM AUTHOR]

Unmixing of remanent magnetization curves, either isothermal remanent magnetization (IRM) or backfield IRM, is widely used in rock magnetic and environmental magnetic studies to discriminate between magnetic coercivity components of different origins. However, the wide range of physical properties of natural magnetic particles gives rise to an ambiguous interpretation of these components. To reduce this ambiguity and provide a straightforward interpretation of coercivity components in terms of domain state, interactions, and constituent magnetic phases, we combined backfield IRM unmixing with unmixing of nonlinear Preisach maps for two typical mid‐latitude northern hemisphere loess‐paleosol sequences. Both backfield IRM and nonlinear Preisach maps unmixing are based on the same non‐parametric algorithm, and provide similar endmembers (EMs) in the two sections studied. The first EM (EM1) has a low median coercivity (∼21 mT) and is a non‐interacting single domain (SD) magnetite/maghemite of pedogenic origin. The second EM (EM2) has a moderate median coercivity (∼60 mT) and is a mixture of pseudo‐single domain/multidomain, SD magnetite/maghemite and non‐interacting SD hematite, all of eolian origin. The same EM1 found in both sections suggests that this component's grain size and coercivity are independent of pedogenesis intensity. The same EM2 indicates that a similar magnetic population is being transported and deposited, irrespective of the dust source area and loess granulometry. The approach outlined here provides strong evidence that non‐parametric backfield IRM unmixing isolates physically realistic EMs. Unmixing nonlinear Preisach maps elucidates these EMs in terms of domain states and their constituent magnetic phases. Plain Language Summary: Magnetic minerals occurring in natural materials carry crucial information about environmental processes. However, since a given material typically contains several magnetic components, the environmental signals it encodes are convoluted. Due to different physical properties of natural magnetic particles, recovering information about each individual process can be a challenging task. One popular method used to differentiate magnetic populations with different origins is numerical unmixing of their coercivity distributions because they are sensitive to characteristics of individual magnetic populations. Coercivity distributions represent the first derivatives of IRM acquisition curves, which are built by exposing a sample to a series of magnetic fields in the laboratory. Generally, there is ambiguity in the interpretation of coercivity components. Therefore, we devised an unmixing method using data sets called non‐linear Preisach maps, built from a sequence of IRM curves that are processed into two‐dimensional diagrams. These data sets give us additional information to that gleaned from coercivity distributions, such as magnetic domain states and particle interaction signatures. We tested this approach on two loess‐paleosol sections located in Southeastern Europe, because they developed in different climatic conditions, and had different dust source areas. Key Points: Non‐parametric remanent magnetization curves unmixing provides physical, though ambiguous, componentsNon‐parametric Preisach maps unmixing resolves this ambiguity by allowing the identification of mineral phases and domain statesIn loess‐paleosol deposits the pedogenic and eolian components are respectively independent of pedogenesis intensity and dust source areas [ABSTRACT FROM AUTHOR]

Resonant ultrasound spectroscopy (RUS) is a powerful method to determine elastic constants with high accuracy and precision from a single measurement of the mechanical resonances of a sample. Conventionally, the quantitative extraction of elastic moduli with RUS assumes free boundary conditions which can often lead to the adoption of unstable sample positioning between ultrasonic transducers that is incompatible with extreme environments like high magnetic fields. We show that, under specific conditions, introducing a small amount of adhesive between a RUS sample and ultrasonic transducers introduces a perturbation to the free resonance condition which can be accounted for by a simple model. This means elastic constants can be determined to within the uncertainty of conventional RUS, but with significant improvements including sample stability and control of sample orientation. We demonstrate the efficacy of this approach with measurements on a range of materials including room temperature measurements on polycrystalline metals, temperature-dependent measurements of the structural phase transition in strontium titanate single crystals, and magnetic field-dependent measurements of magnetic phase transitions in gadolinium polycrystals up to 14 T. [ABSTRACT FROM AUTHOR]

Arc magnetic field analysis is a valuable approach for assessing the stability of the arc welding process, yet existing methods lack the ability to effectively quantify the disorder within the process. Through an investigation into the characteristics of the arc magnetic field signal, it was observed that the occurrence of low-frequency random fluctuations in arc magnetic field power, induced by unstable factors such as bubbles or short circuits, contributed to increased complexity and randomness in the arc magnetic field signals. To visualise the arc magnetic field signals in a time-frequency domain, a spectrogram was employed, revealing a strong correlation between the distribution of maximum power spectral density (PSD) in the spectrogram and the stability of the arc welding process. Furthermore, a novel method based on sample entropy was introduced to provide a quantitative measure of this relationship. A comprehensive quantitative assessment indicator called arc magnetic field sample entropy (AMFSE) was proposed. This indicator effectively mitigates the influence of varying parameters on the quantitative results, enabling a more accurate and consistent representation of the stability of the arc welding process. The proposed method was validated through testing, yielding an accuracy rate exceeding 90%. [ABSTRACT FROM AUTHOR]

We perform systematic studies on the magnetic and magnetotransport properties of Fe1/3NbS2 single crystal. Results show that Fe1/3NbS2 is an antiferromagnet with strong perpendicular magnetocrystalline anisotropy even in the paramagnetic state. The Fe1/3NbS2 nanoplate exhibits exotic magnetotransport characteristics with variation of temperature and magnetic field in the vicinity of Néel temperature. The temperature dependence of resistivity indicates that the magnetic field has a substantial effect on the Néel order of Fe1/3NbS2, and an intermediate phase occurs before the sample enters into the antiferromagnetic state. It is the field- or temperature-induced antiferromagnetic–intermediate phase and intermediate phase–paramagnetic phase transitions that lead to the novel magnetotransport characteristics in the vicinity of Néel temperature. The findings in this work will promote future studies based on two-dimensional antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

Cryogenic refrigeration technology based on magnetocaloric effects plays a critical role in a variety of technological applications. In this paper, we report the cryogenic magnetocaloric effects of a series of sodium-rare earth fluoride samples (Ln = Gd, Tb, Dy, Ho, Er, Tm, Yb) synthesized by the solid-state reaction method. These compounds all crystallize in a hexagonal crystal structure. Down to 2 K, no magnetic ordering was detected, while all compounds show negative Curie–Weiss temperatures indicative of strong antiferromagnetic coupling. Magnetic fields effectively suppress the magnetic fluctuations, leading to a maximum magnetic entropy change of −56 J kg−1 K−1 in NaGdF4 at the magnetic field change from 0 to 50 kOe. These series of compounds are potentially excellent magnetic refrigerants at low temperatures. [ABSTRACT FROM AUTHOR]

We perform systematic studies on the magnetic and magnetotransport properties of Fe1/3NbS2 single crystal. Results show that Fe1/3NbS2 is an antiferromagnet with strong perpendicular magnetocrystalline anisotropy even in the paramagnetic state. The Fe1/3NbS2 nanoplate exhibits exotic magnetotransport characteristics with variation of temperature and magnetic field in the vicinity of Néel temperature. The temperature dependence of resistivity indicates that the magnetic field has a substantial effect on the Néel order of Fe1/3NbS2, and an intermediate phase occurs before the sample enters into the antiferromagnetic state. It is the field- or temperature-induced antiferromagnetic–intermediate phase and intermediate phase–paramagnetic phase transitions that lead to the novel magnetotransport characteristics in the vicinity of Néel temperature. The findings in this work will promote future studies based on two-dimensional antiferromagnetic spintronics. [ABSTRACT FROM AUTHOR]

The magnetic properties, critical behavior, and magnetocaloric effect of perovskite NdMnO3 are studied. The Nd ordering is induced by the Mn ferromagnetic component with antiferromagnetic coupling with each other and then magnetization reversal occurs due to Mn moments reorientation induced by the ordering Nd moments, which explains the phenomenon of negative magnetization at low temperatures. The critical behavior of NdMnO3 is studied using Kouvel–Fisher and self-consistent methods. The results show that the Kouvel–Fisher method is reliable and critical exponents are coming out as β = 0.462 for TC = 11.15 K, γ = 1.041 for TC = 11.42 K, δ = 3.252 by critical isotherm analysis. Magnetic exchange distance may decay as J (r) ≈ r − 4.563 , that is, somewhere between the three-dimensional Heisenberg model and the mean field model. Remarkably, three temperature transitions and the corresponding three extremum values including positive and negative entropy change are observed in NdMnO3, which is different from previous reports on NdMnO3. A positive entropy change as 3.82 J/kg K at 10–15 K for μ0ΔH = 50 kOe and a negative entropy change as −0.557 J/kg K at around 8 K for μ0ΔH = 5 kOe are found, which can be put down to a fast magnetization change of NdMnO3 because of the Nd moments ordering and Mn moments reorientation. Besides, an entropy change of 1.22 J/kg K is found for μ0ΔH = 50 kOe at 80–85 K, which is corresponding to the Mn ferromagnetic ordering temperature. The relative cooling power of NdMnO3 reaches 105.9 J/kg, making it a promising candidate in the field of magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The influence of Co and Ni ion doping on the crystal structure, phase transitions, and magnetic properties of the Fe7Se8 system has been investigated. The compounds studied are (Fe0.987Ni0.013)7Se8, (Fe0.955Ni0.045)7Se8, (Fe0.915Ni0.085)7Se8, (Fe0.89Ni0.11)7Se8, (Fe0.79Ni0.21)7Se8, (Fe0.975Co0.025)7Se8, (Fe0.951Co0.049)7Se8, and (Fe0.91Co0.09)7Se8 as well as the parent compound Fe7Se8. The crystals are grown using a modified Bridgman method and exist as a hexagonal NiAs-like structure with an ordered distribution of Fe vacancies that determine their magnetic properties. The substitution effect, inducing a systematic decrease in the unit-cell volume due to the ionic radii of doping ions being smaller than the radii of Fe2+ ions, is a source of chemical pressure, acting on the magnetic subsystem and determining the magnetic ordering temperature TC and the spin-reorientation temperature (TSRT). As the most important result of this paper, it was shown that hydrostatic and chemical pressures are strongly correlated in the investigated system. The character of magnetic phase transitions has been designated in the vicinity of TC and TSRT temperatures, and the magnetic entropy change ΔSm and refrigeration potential magnitudes have been determined for this temperature range. These magnetocaloric parameters were shown to depend strongly on chemical pressure. A phenomenological model developed based on the experimental measurements demonstrated that the magnetic properties of the system depend strongly on the crystal field acting on Fe2+ ions and the ratio of the numbers of Fe2+ and Fe3+ ions. [ABSTRACT FROM AUTHOR]

In this work, we report the role of turbulence (measured by the |$^{12}\mathrm{ CO}$| linewidth, |$\Delta V$|⁠) on the offset between the orientation of local magnetic field in the low-density regions of dark clouds (⁠|$\theta ^{\mathrm{ env}}_\mathrm{ B}$|⁠) and the position angle of the Galactic Plane (GP; |$\theta _{\mathrm{ GP}}$|⁠) in 15 low-mass isolated molecular clouds. We find a dependency of |$\Delta V$| on offset, (⁠|$\theta _{\mathrm{ off}} =|\theta ^{\mathrm{ env}}_\mathrm{ B}-\theta _{\mathrm{ GP}}|$|⁠), represented by a second-order polynomial equation, |$\theta _{\mathrm{ off}}=(3.328 \pm 1.187) {\Delta V}^2 - (0.991 \pm 5.541) {\Delta V} + (4.767 \pm 5.309)$|⁠. In regions where the majority of low turbulence is observed, characterized by |$\Delta V \ \lt\ 3.1 \ \mathrm{ km\,s}^{-1}$|⁠ , the envelope magnetic fields closely align with the orientation of the GP (⁠|$\theta _{\mathrm{ off}}\ \lt\ 20^\circ$|⁠). Conversely, in areas exhibiting high turbulence with |$\Delta V \ \gt\ 3.1 \ \mathrm{ km\,s}^{-1}$| (for clouds CB130 and CB188), the envelope magnetic field tends to misalign with the GP (⁠|$\theta _{\mathrm{ off}}\ \gt\ 50^\circ$|⁠). This suggests that turbulence could be one of the important factors influencing the alignment of the local magnetic field with the GP. We have also explored the potential link between gas density of clouds (⁠|$\rho$|⁠) and turbulence (⁠|$\Delta V$|⁠) for the first time, utilizing data from 10 isolated clouds. This analysis suggests a possible correlation, with the observed trend quantified as, |$\Delta V \propto \rho ^{-0.19}$|⁠. [ABSTRACT FROM AUTHOR]

In this research article, the irreversibility of Jeffery fluid in mixed convective flow with inclined channel under the influence of Navier‐slip condition is analyzed. The effects of Hall current, Soret number, and an inclined magnetic field are taken into account. The spectral quasi‐linearization method (SQLM) is used to solve the governing equations after transforming them into a dimensionless form. The impacts of various parameters on velocity, temperature, and concentration are examined graphically. With the use of tabular data, variations in skin friction, the Nusselt number, and the Sherwood number are also discussed. Our findings indicate that entropy production increases with higher values of the magnetic parameter, Hall current, and inclination angle. Conversely, we have observed an opposing trend with an increased value of slip condition at the left plate and the Jeffrey fluid parameter. [ABSTRACT FROM AUTHOR]

The issue of whether CoCrFeNi is a single-phase or dual-phase high-entropy alloy (HEA) has long been in dispute. In this study, CoCrFeNi has been verified to be a dual-phase HEA composed of dendritic phases with an FCC structure and inter-dendritic phases with a BCC structure. The BCC phases within inter-dendritic regions are identified as Cr3O oxides which form inevitably under the arc-melting process. Undercooling treatment under a strong magnetic field can regulate the composition and precipitation of the BCC phase, refine the grain size, and enhance the solid solubility, consequently, the mechanical performances of CoCrFeNi HEA are effectively enhanced. [ABSTRACT FROM AUTHOR]

Based on theoretical calculations and experiments, the crystal structure, electronic structure, magnetism, and magnetocaloric effect (MCE) of the Ho5B2C5 compound have been systematically investigated. The Ho5B2C5 compound with a typical metallic nature was found to crystallize in a tetragonal structure belonging to space group P4/ncc (No. 130), and its magnetic ground state was identified as ferromagnetic (FM) ordering based on theoretical and experimental results. Additionally, a second-order magnetic phase transition from FM to paramagnetic around approximately 27 K was observed in the Ho5B2C5 compound, resulting in a large MCE. Under varying magnetic fields (Δ H) from 0 to 7 T, the maximum magnetic entropy change (− Δ S M max ), refrigeration capacity (RC), and δ TFWHM are 21.3 J/kg K, 1001.6 J/kg, and 60.2 K (a wide temperature range from 15.2 to 75.4 K), respectively. The outstanding MCE performance of the Ho5B2C5 compound is expected to facilitate the progress of magnetic refrigeration for hydrogen liquefaction. [ABSTRACT FROM AUTHOR]

In this current study, we present a detailed investigation on the structural, magnetic, magnetocaloric and electrical properties for La0.4Ag0.1Ca0.5MnO3 (S1) and La0.5Ca0.4Ag0.1MnO3 (S2) polycrystallines samples prepared using the well-known sol–gel method. Our analysis of X-ray diffraction, employing Rietveld refinement, reveals that these samples crystallize in the orthorhombic structure with Pnma space group. The results demonstrated that magnetization measurements as a function of temperature, under different magnetic fields for the sample (S1), exhibit two distinct phase transitions at TC1 = 48 K and TC2 = 186 K, whereas sample (S2) displays a single transition at 261 K. Based on the magnetic field dependence of magnetization, M(H), and applying the thermodynamic Maxwell equation, the magnetic entropy change |ΔSm| of the studied samples (S1) and (S2) was determined. Electrically, we observed an upturned region of resistance at low temperature, and this recovery of the resistance is significantly influenced by the external magnetic field. [ABSTRACT FROM AUTHOR]

Composite multiferroic materials were prepared using the conventional ceramic double sintering process, with composition of Ґ BaTiO3/(1 − Ґ) Cu0.3Ni0.1Zn0.6Fe2O4, where Ґ represents the mass fraction of the ferroelectric phase ranging from 0.3 to 0.9. The behavior of the bulk composites under external dynamic magnetic and electric fields was studied as a function of the ferroelectric phase content. The objective of this work is to establish a relationship between the irreversibility process and magnetic and electrical losses in composite magnetoelectric materials. Experimental measurements were correlated with the entropy production of materials. The results allow us to infer that in the explored frequency range (from 1 MHz to 1.8 GHz), entropy production not only decreases as the ferroelectric phase content increases but is also related to the magnetic losses. [ABSTRACT FROM AUTHOR]

To optimize the formation of the magnetocaloric 1:13 phase in La(Fe,Si)13-based compounds, a method to improve the preparation process and promote the practical application of magnetic refrigeration is proposed. The LaFe10.9Co0.7Si1.4 and LaFe13.1Co0.7Si1.4 samples were plastically deformed to different degrees by cold compression at room temperature. Subsequently, grain structure, phase composition, and magnetocaloric effects were systematically investigated. The results demonstrated that the pre-deformation process can effectively increase the number of grains per unit volume and homogenize the grain size. Using the same annealing temperature and time, the 1:13 phase in the pre-compressed samples was much higher than that in the uncompressed samples, whereas the compression deformation did not cause an uneven elemental distribution. Compared to LaFe13.1Co0.7Si1.4, the LaFe10.9Co0.7Si1.4 compound obtained by the same preparation process has a higher magnetocaloric phase ratio. After short annealing for 3 days, the Curie temperature (TC) of 40% pre-deformed LaFe10.9Co0.7Si1.4 sample reaches 303 K, and the magnetic entropy change of 5.30 and 10.55 J/kg K under 2 and 5 T magnetic fields is observed. The good magnetic refrigeration-related performance makes the 40% pre-deformed LaFe10.9Co0.7Si1.4 alloy a potential candidate for room temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

In this article, the Caputo Fabrizio fractal fractional order derivatives operator with an exponential kernel was employed to examine the radiative heat and mass transfer characteristics of time dependent flow with variable fluid viscosity, induced magnetic field, Soret and Dufour effects. The local mathematical model for the flow problem is formulated by take into account the impacts of thermal radiation, heat source, and viscous dissipation. The governing equations in-terms of fractal fractional model with an exponential kernel were solved numerically using finite difference method. The influence of flow variables such as induced magnetic field, concentration field, entropy rate, thermal field, and velocity field profiles against the pertinent parameters are discussed through graphs. Increase the values of magnetic Prandtl number results to rises of induced magnetic field. Higher Dufour number significantly grows the thermal field. The fractal fractional parameters enhance the velocity field, thermal field, Bejan number, entropy rate, concentration field and induced magnetic field profiles. The velocity field profiles recede with higher values of fluid variable viscosity parameter whereas the thermal field and induced magnetic field has an opposite effect. Larger Soret number amplifies the concentration field. Increase of Brinkman number, thermal radiation parameter, and magnetic Prandtl number intensifies the entropy generation rate. Increases of Brinkman number, magnetic Prandtl number, Soret number and Dufour number leads to a decrease of Bejan number whereas Bejan number rises with an increase of thermal radiation parameter and heat source. [ABSTRACT FROM AUTHOR]

Hybrid nanofluids have emerged as a promising field of research in recent years, finding applications in various industries and sectors. The entropy generation and impact of an inclined magnetic field on a water-Ethylene Glycol (50:50) mixture-based nanofluid over a poignant thin needle has been investigated under slip conditions. The flow is swotted using thermal and velocity slip boundary conditions. The numerical effects of an inclined magnetic field on the flow of ferrous and aluminum oxide nanoparticles in a hybrid nanoliquid with as base fluids have been examined. The non-dimensional ODEs along with boundary conditions are solved by numerical technique based on the Runge–Kutta fourth-order method. Velocity profile has been analyzed for the magnetic parameter, inclined angle and volume fractions. The Bejan number provides insights into the balance between heat transfer and entropy generation in a system. From the numerical values of skin friction coefficient and Nusselt number, it is analyzed that Al 2 O3 possesses 1.01% and 1.06% of high heat transfer rate and high surface drag force than Fe 3 O4. Heat transfer profile has been analyzed for entropy generation and the Bejan number. The applications of hybrid nanofluids are vast, and one specific area where they can be utilized is in horizontal needle systems. [ABSTRACT FROM AUTHOR]

The scaling behavior of the entanglement entropy of droplet states in Heisenberg spin-1/2 XXZ model defined on a strip of width M under the presence of a non-negative background magnetic field is investigated. Without any assumptions on V, a logarithmically corrected area law is shown. Assuming that the values of V are i.i.d. random variables, an area law in expectation is obtained. [ABSTRACT FROM AUTHOR]

We have systematically studied the crystal structure, cryogenic magnetic properties and MCE in RE 2 MgTiO 6 (RE = Tb, Dy, Ho and Er) DP oxides. The four RE 2 MgTiO 6 samples are all found to crystallize in a monoclinic DP structure (P 2 1 /n space group). The Néel temperature (T N) are found to be 4.7, 4.5, 3.1 and 2.1 K for RE 2 MgTiO 6 (RE = Tb, Dy, Ho and Er) DP oxides, respectively. Moreover, the maximum magnetic entropy change (-Δ S M max) together with relative cooling power (RCP) near T N under a magnetic field change (ΔH) of 0–7 T are evaluted to be 16.85, 360.59 for Tb 2 MgTiO 6 , 17.72, 381.05 for Dy 2 MgTiO 6 , 15.92, 398.14 for Ho 2 MgTiO 6 and 22.95 J/kg K, 459.09 J/kg for Er 2 MgTiO 6 , respectively. The excellent cryogenic MCE suggest that RE 2 MgTiO 6 (RE = Tb, Dy, Ho and Er) DP oxides can be used as a promising candidate material for cryogenic magnetic refrigeration. [ABSTRACT FROM AUTHOR]

The effects of doping, hydrostatic pressure, and thermal quenching on the phase transitions and magnetocaloric properties of the Mn1−xCoxNiGe system have been investigated. Cobalt doping on the Mn site shifted the martensitic structural transition toward lower temperature until it was ultimately absent, leaving only a magnetic transition from a ferromagnetic (FM) to a paramagnetic (PM) state in the high-temperature hexagonal phase. Co-occurrence of the magnetic and structural transitions to form a first-order magnetostructural transition (MST) from the FM orthorhombic to the PM hexagonal phase was observed in samples with 0.05 < x < 0.20. An additional antiferromagnetic–ferromagnetic-like transition was observed in the martensite phase for 0.05 < x < 0.10, which gradually vanished with increasing Co concentration (x > 0.10) or magnetic field (H > 0.5 T). The application of external hydrostatic pressure shifted the structural transition to lower temperature until an MST was formed in samples with x = 0.03 and 0.05, inducing large magnetic entropy changes up to −80.3 J kg−1 K−1 (x = 0.03) for a 7-T field change under 10.6-kbar pressure. Similar to the effects of the application of hydrostatic pressure, an MST was formed near room temperature in the sample with x = 0.03 by annealing at high temperature (1200 °C) followed by quenching, resulting in a large magnetic entropy change of −56.2 J kg−1 K−1. These experimental results show that the application of pressure and thermal quenching, in addition to compositional variations, are effective methods to create magnetostructural transitions in the MnNiGe system, resulting in large magnetocaloric effects. [ABSTRACT FROM AUTHOR]

In this paper, we present structural, magnetic, magnetocaloric, and critical study of perovskite La0.7Ag0.2Bi0.1MnO3 (LABMO) nanocrystalline compound synthesized by the sol–gel method. Temperature dependent magnetization measurements reveal the significant suppression of ferromagnetism in the LABMO sample upon Bi-doping on a La-site. The downturn in inverse magnetic susceptibility (χ−1) observed just above TC (236 K) in the paramagnetic regime corroborates the presence of short-range ferromagnetic correlations, which is the characteristic of the Griffith like phase below 270 K. The deviation from linear paramagnetic behavior in χ−1 implies the strong Griffith singularity. Furthermore, we have employed an integrated Maxwell's thermodynamic relation numerically and used isothermal magnetization data to determine the change in magnetic entropy at various magnetic fields. For a magnetic field change of 5 T, the value of maximum magnetic entropy change is found to be ∼6 J kg−1 K−1. We have also explored the critical behavior of the LABMO sample at transition temperatures using different theoretical models. The value of exponents β, γ, and δ does not fall into any known universality class. Despite this, the scaling relations show that interactions are renormalized around the Curie temperature (TC). The exponent n ≤ 2 extracted from field dependency on the magnetic entropy change confirms the second-order phase transition in LABMO. [ABSTRACT FROM AUTHOR]

In this paper, we present structural, magnetic, magnetocaloric, and critical study of perovskite La0.7Ag0.2Bi0.1MnO3 (LABMO) nanocrystalline compound synthesized by the sol–gel method. Temperature dependent magnetization measurements reveal the significant suppression of ferromagnetism in the LABMO sample upon Bi-doping on a La-site. The downturn in inverse magnetic susceptibility (χ−1) observed just above TC (236 K) in the paramagnetic regime corroborates the presence of short-range ferromagnetic correlations, which is the characteristic of the Griffith like phase below 270 K. The deviation from linear paramagnetic behavior in χ−1 implies the strong Griffith singularity. Furthermore, we have employed an integrated Maxwell's thermodynamic relation numerically and used isothermal magnetization data to determine the change in magnetic entropy at various magnetic fields. For a magnetic field change of 5 T, the value of maximum magnetic entropy change is found to be ∼6 J kg−1 K−1. We have also explored the critical behavior of the LABMO sample at transition temperatures using different theoretical models. The value of exponents β, γ, and δ does not fall into any known universality class. Despite this, the scaling relations show that interactions are renormalized around the Curie temperature (TC). The exponent n ≤ 2 extracted from field dependency on the magnetic entropy change confirms the second-order phase transition in LABMO. [ABSTRACT FROM AUTHOR]

In the present investigation, computational study of magneto-laminar flow mixed convection and entropy generation using two binary (TiO2-CNT/kerosene), (TiO2-Gr/kerosene) and ternary hybrid (TiO2-CNT-Gr/kerosene) nanofluids inside three‐dimensional horizontal annular duct saturated with porous media are numerically investigated. The exterior cylinder's surface is uniformly heated through a uniform heat flux, whereas the interior cylinder's surface is adiabatic. The numerical solutions are obtained using the finite volume method (FVM). The single-phase and thermal equilibrium models are adopted. The control parameters are: Darcy number (10−4 ≤ Da ≤ 10−1), Hartmann number (0 ≤ Ha ≤ 50), magnetic field inclination (ψ = 0°, ψ = 90°), Grashof number (Gr = 106), and nanoparticle concentrations 5%. The study of hydrodynamic and thermal behavior reveals that significant improvements in heat transfer are obtained when a magnetic field is applied horizontally and in the same direction as the flow. At the same time, it involves retardation on the hybrid nanofluids flow. Moreover, when the Darcy number increases, the heat transfer rate reduces by 24%, 23%, and 21% for TiO2-CNT-graphene/kerosene, TiO2-CNT/kerosene, and TiO2-Graphene/kerosene, respectively. No significant influence was observed on heat transfer when the applied magnetic field was perpendicular to the flow direction and in the same direction as the buoyancy force. [ABSTRACT FROM AUTHOR]