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The manuscript explores the electromagnetic and magnetocaloric characteristics of the intermetallic compound Gd 2 Cu 2 C d. One of the key findings is that Gd2Cu2Cd possesses a magnetic moment of approximately 7.13 μB. The simulated magnetic properties illustrate a second-order phase transition from ferromagnetic (FM) to paramagnetic (PM) occurring at approximately 130 K. This material exhibits a substantial magnetocaloric effect (MCE) across various external magnetic field strengths. To be more specific, this transition occurs at an external magnetic field of 4.0 T, in particular, at an external magnetic field of 4.0 T, the extreme magnetic entropy change ( Δ S mag ) is measured at 3.58 J/kg.K, and the relative cooling power (RCP) reaches 28 J/kg. Notably, with an increase in the external magnetic field, the maximum value of ( ΔS mag ) increases significantly, and the Curie temperature ( T C ) shifts toward lower temperatures. These results suggest that Gd 2 Cu 2 Cd has significant potential for applications in magnetic refrigeration that leverage the magnetocaloric effect. [ABSTRACT FROM AUTHOR]

In this research, the single-phase tetragon NdMn2-xAgxSi2 (0 ≤ x ≤ 0.4) alloys were prepared. It was found that the phase transition temperature was decreased by evaluating Ag substitution, which was attributed to the enhancement of orbital hybridization. The thermomagnetic hysteresis disappears for x ≥ 0.2. For Δμ0H of 0–7 T, the values of the maximum magnetic entropy change (the relative cooling power) are 22.2 J/kgK (420.7 J/kg), 20.1 J/kgK (500.5 J/kg), 19.9 J/kgK (552.8 J/kg) and 12.0 J/kgK (300.0 J/kg) in NdMn2-xAgxSi2 (x = 0, 0.2, 0.3 and 0.4) alloys. The XPS valence band spectra indicate that the density of electron and the hybridization effect is enhanced by increasing the substitution amount of Ag. This is attributed to the fact that the atomic radius of Ag is larger than that of Mn, resulting in the strengthening of the covalent bond between Ag and Si. [ABSTRACT FROM AUTHOR]

Spinel ferrites are magnetic oxide materials with potentials to promote green technology in magnetic refrigeration which is known to be economically clean, energy saving and efficient. Maximum magnetic entropy change of spinel ferrites decides and controls the applicability as well as the strength of spinel ferrite magnetic oxide since it measures the hugeness of magnetocaloric effect. However, experimental determination of maximum magnetic entropy change requires intensive procedures, costly equipment and consumes appreciable time. Intelligent models are presented in this work using spinel-ferrite-molecular-based descriptors such as the ionic radii of spinel ferrites constituents, applied magnetic field and their concentrations. The developed intelligent models for prediction of spinel ferrite maximum magnetic entropy change include extreme learning machine (ELM) and hybrid genetic-algorithm-coupled support vector regression (GSVR). The developed ELM model has correlation coefficient (CC) and mean absolute error (MAE) of 98.45% and 0.117 J/kg/K, respectively, while the developed GSVR model has CC of 80.87% and MAE of 0.129 J/kg/J. The developed ELM model which is based on empirical risk minimization principle shows better performance over GSVR model that premises on structural minimization risk principle with improvement of 0.06%, 17.86% and 8.765% using root mean square error, CC and MAE yardsticks, respectively. Closeness of the estimates of the developed models with the experimental values is a strong indication of the potentials of the proposed intelligent methods in facilitating practical implementation of magnetic cooling refrigeration to solve energy crisis which promote efficiency and environmental friendliness. [ABSTRACT FROM AUTHOR]

To simulate the magnetocaloric effect (MCE) of a HoCo2 sample, a phenomenological model (PM) is used. MCE parameters are inferred from PM as the result of modelling for magnetization vs. temperature in 0.5 T. The HoCo2 exhibits two consecutive conventional MCEs with cooling via adiabatic demagnetization. HoCo2 exhibits double peak MCE behaviour. It is recommended that HoCo2 use it as a useful MR material over a temperature range spanning a significant temperature range of 0–140 K. Consequently, HoCo2 is appealing for MR because its MCE spans a wide temperature range, particularly liquefaction of nitrogen and hydrogen. [ABSTRACT FROM AUTHOR]

To simulate the magnetocaloric effect (MCE) of a HoCo2 sample, a phenomenological model (PM) is used. MCE parameters are inferred from PM as the result of modelling for magnetization vs. temperature in 0.5 T. The HoCo2 exhibits two consecutive conventional MCEs with cooling via adiabatic demagnetization. HoCo2 exhibits double peak MCE behaviour. It is recommended that HoCo2 use it as a useful MR material over a temperature range spanning a significant temperature range of 0–140 K. Consequently, HoCo2 is appealing for MR because its MCE spans a wide temperature range, particularly liquefaction of nitrogen and hydrogen. [ABSTRACT FROM AUTHOR]

Quantum description of the isothermal and adiabatic magnetocaloric effect (MCE), thermomagnetic properties, and energy spectra of three diatomic molecules, namely: lithium hydride (LiH), titanium hydride (TiH), and scandium hydride (ScH), was examined with Deng-Fan-Screened Coulomb Potential using the Greene-Aldrich approximation to the centrifugal term. The numerical solutions of the proposed potential with and without the magnetic and AB flux fields obtained reveal that the combined impacts of the magnetic and AB flux fields completely remove the degeneracy of the energy spectra and control the behaviour of the MCE by acting as a regulating factor to cool or heat the MCE. Also, the proposed potential reduces to three exceptional cases, and the thermomagnetic plots obtained for the analysed dimer molecules agreed perfectly with previous work. This research has the potential to be applied in molecular physics and MCE studies for a variety of molecules. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect in RE 11 Co 4 In 9 (RE = Tb, Er) has been studied by means of magnetometric measurements in the function of temperature and applied magnetic field. The maximum magnetic entropy change ( − Δ S M max ) at magnetic flux density change ( Δ μ 0 H) 0–9 T has been determined to be 5.51 J kg − 1 K − 1 at 47.4 K for Tb 11 Co 4 In 9 and 14.28 J kg − 1 K − 1 at 12.3 K for Er 11 Co 4 In 9 , while temperature averaged entropy change (TEC) with 3 K span equals 5.50 and 14.14 J kg − 1 K − 1 for RE = Tb and Er, respectively. The relative cooling power (RCP) and refrigerant capacity (RC) equal respectively 522.1 and 391.2 J kg − 1 in Tb 11 Co 4 In 9 and 605.2 and 463.1 J kg − 1 in Er 11 Co 4 In 9 . [ABSTRACT FROM AUTHOR]

The deficiency of materials with coexisting transport and magnetocaloric effect has prevented the development of intermetallic-based magnetic refrigeration applications. Therefore, intermetallic alloys are non-toxic, inexpensive, and low density. The presents work investigates the magnetic, magnetocaloric, and thermoelectric properties of the intermetallic LaMn2Si2 compound by using the first-principles calculations and Monte Carlo simulations. From the Ab initio calculation, the exchange coupling and anisotropy interactions are calculated. Also, the magnetic and magnetocaloric properties are determined using Monte Carlo simulations. It is found that the intermetallic LaMn2Si2 compound exhibits a second-order ferromagnetic-paramagnetic phase transition around TC ∼ 319 K , this value of temperature is in good agreement with the experimental value. Finally, the thermoelectric properties are discussed. Our results improve that this material is applicable for magnetic refrigeration at Curie temperature. [ABSTRACT FROM AUTHOR]

The influence of the synthesis method on structural, magnetic and magnetocaloric properties of the La0.5Ca0.5Mn0.95V0.05O3 compound has been investigated. The compound was prepared by glycine nitrate process (GNP) and compared to counterparts obtained with solid-state route (S-S) and ball milling (B-M). The structural analysis shows a pure and single-orthorhombic crystalline phase for the GNP compound. A secondary phase LaVO4 was detected for S-S and B-M samples. From magnetization versus temperature analysis, different magnetic behaviors were distinguished when moving from one technique to another. The nature of transition was determined and a crossover from second order to first-order magnetic transition was observed with the decrease of crystallite size. Landau theory was performed to confirm the order of magnetic transition of the sample consistent with the Banerjee criterion. The magnetic entropy change (ΔSm) and the relative cooling power RCP, which decreased by reducing the particle size, were calculated. [ABSTRACT FROM AUTHOR]

We report first-principles calculations on the electronic, magnetic, and magnetocaloric properties of the perovskite metal compound Mn3GeC. We have studied this compound using a combination of density functional theory calculations (DFT) and Monte Carlo methods. The metallic perovskite Mn3GeC materials have a secondary ferromagnetic-paramagnetic transition around TC = 330 K. Our calculations show that this compound is more stable in the equilibrium state of the ferromagnetic network, estimated in agreement with the experimental parameter. The results of the simulation reveal that the Mn3GeC structure behaving of metallic nature; using calculations of first-principles, the magnetic and magnetocaloric properties have been calculated. Additionally, the magnetization and the susceptibility have been determined and the obtained critical temperature TC is in good agreement with the experimental results. The magnetic entropy and the relative cooling power for different external magnetic fields are obtained around TC. [ABSTRACT FROM AUTHOR]

In this work, a phenomenological model (PM) is used to simulate the magnetocaloric effect (MCE) of GdMn1-xCrxO3 (0 ≤x ≤0.4) (GMCO) samples through the modelling of experimental isofield thermo-magnetization curves. The results showed that the MCE of GMCO samples depends strongly on Cr content, achieving a conventional MCE for low Cr content (level of doping x ≤ 0.3). However, the MCE of a higher Cr content sample has an inverse MCE. The behaviour of MCE in GMCO samples indicated that GMCO compounds are interesting magnetocaloric materials and can fruitfully be functioned as cryogenic magnetic refrigerants below 40 K especially in radiation detectors for outer space research. [ABSTRACT FROM AUTHOR]

In this work, a phenomenological model (PM) is used to simulate the magnetocaloric effect (MCE) of GdMn1-xCrxO3 (0 ≤x ≤0.4) (GMCO) samples through the modelling of experimental isofield thermo-magnetization curves. The results showed that the MCE of GMCO samples depends strongly on Cr content, achieving a conventional MCE for low Cr content (level of doping x ≤ 0.3). However, the MCE of a higher Cr content sample has an inverse MCE. The behaviour of MCE in GMCO samples indicated that GMCO compounds are interesting magnetocaloric materials and can fruitfully be functioned as cryogenic magnetic refrigerants below 40 K especially in radiation detectors for outer space research. [ABSTRACT FROM AUTHOR]

In this work, a phenomenological model (PM) is used to simulate the magnetocaloric effect (MCE) of GdMn1-xCrxO3 (0 ≤x ≤0.4) (GMCO) samples through the modelling of experimental isofield thermo-magnetization curves. The results showed that the MCE of GMCO samples depends strongly on Cr content, achieving a conventional MCE for low Cr content (level of doping x ≤ 0.3). However, the MCE of a higher Cr content sample has an inverse MCE. The behaviour of MCE in GMCO samples indicated that GMCO compounds are interesting magnetocaloric materials and can fruitfully be functioned as cryogenic magnetic refrigerants below 40 K especially in radiation detectors for outer space research. [ABSTRACT FROM AUTHOR]

In our present work, La0.75Ca0.25–xNaxMnO3 (0 ≤ x ≤ 0.10) samples were synthesized by the flux method. The structural and the magnetocaloric properties were studied. The crystallographic study indicates that our samples crystallize in the orthorhombic structure, with Pbnm space group. The magnetocaloric properties have been theoretically studied and compared with the experimental results, under low magnetic field of 0.05 T. It has been found that the simulated data M(T), −ΔSM (T), ΔTad and ΔCP,H (T) are in good agreement with the experimental one. In addition, the magnetocaloric effect of Na+ in our system is important and beneficial for manipulating magnetocaloric refrigeration. [ABSTRACT FROM AUTHOR]

We report a study of the metamagnetic transition and magnetocaloric effect in the ternary Ni45Mn42In13 Heusler alloy system. We also investigate the structural and magnetic properties of the alloy. The crystal structure exhibited a mixture phase of martensite and austenite at room temperature which are typical for Heusler alloys. The thermomagnetization curves have martensitic and magnetic transition near room temperature and with a quite large magnetization value under 5 T applied external magnetic field. The obvious reversible metamagnetic behavior was seen between 285 and 295 K temperatures. The isothermal M–H curves also confirmed the metamagnetic transition and provided the magnetocaloric effects by Maxwell relations. This system underwent an austenite–martensite phase transition and the change in magnetic entropy was found to be quite large across this martensitic transition, so this led to an inverse magnetocaloric effect. Significant maximum magnetic entropy was obtained under 5 T applied magnetic field. [ABSTRACT FROM AUTHOR]

The MnNiFeGe alloy is prepared by high-pressure annealing method. It is found that the martensitic transformation temperature after high-pressure annealing of this alloy decreases with the increasing thermal hysteresis. Besides, another magnetic phase transition above the martensitic transformation is observed, which is due to the existence of a large amount of retained austenite induced by high-pressure annealing. As a result, this alloy shows two positive magnetic entropy change peaks, corresponding to the ferromagnetic phase transition of the austenite and the magnetic martensitic transformation, respectively. The magnetic phase transitions, the variable-temperature crystal-structure evolution, and the magnetocaloric properties of this alloy are investigated in detail. [ABSTRACT FROM AUTHOR]

The dendritic iron (III) complex of the third generation (3-K2.10-(FeCl3)9) has been synthesised by complex formation between metal salt and organic ligand and studied. The structural characterisation and mesomorphic properties of the synthesised dendritic complex were investigated by FT-IR spectroscopy, X-ray diffraction measurements, polarising optical microscopy, and differential scanning calorimetry. It was shown that the given complex forms a columnar (Colh) mesophase with the transition to glass state upon cooling. The specific heat capacity of the complex was determined for the first time. The temperature dependencies of the specific heat capacity of the ligand and Fe(III) complex with the third-generation dendrimer show maxima that indicate a 'crystal – mesophase' transition. In order to determine the magnetocaloric effect, magnetisation experiments at fields from 0 to 1.0 T were performed from 263 to 358 К. The temperature dependence of the magnetocaloric effect is extreme. In the temperature range 340 – 350 К there is a sharp maximum indicating a magnetic phase transition. A correlation was found between the 'crystal – mesophase' transition and magnetic phase transition of the Fe(III) complex. The experimentally discovered fact of the existence of the liquid crystalline phase and the spin crossover in the same temperature region suggests the use of this compound in high-tech industries. [ABSTRACT FROM AUTHOR]

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB2. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho1-xDyxB2 alloys (x = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature (TC) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |ΔSM| and adiabatic temperature change ΔTad showed a gradual decrease. On the other hand, due to the presence of successive transitions in these alloys, the peak height of the above magnetocaloric properties tends to be kept in a wide temperature range, leading to a relatively robust figure of merit in a wide temperature span. These alloys could be interesting candidates for magnetic refrigeration in the temperature range of 10–60 K. [ABSTRACT FROM AUTHOR]

Recently, a massive magnetocaloric effect near the liquefaction temperature of hydrogen has been reported in the ferromagnetic material HoB2. Here we investigate the effects of Dy substitution in the magnetocaloric properties of Ho1-xDyxB2 alloys (x = 0, 0.3, 0.5, 0.7, 1.0). We find that the Curie temperature (TC) gradually increases upon Dy substitution, while the magnitude of the magnetic entropy change |ΔSM| and adiabatic temperature change ΔTad showed a gradual decrease. On the other hand, due to the presence of successive transitions in these alloys, the peak height of the above magnetocaloric properties tends to be kept in a wide temperature range, leading to a relatively robust figure of merit in a wide temperature span. These alloys could be interesting candidates for magnetic refrigeration in the temperature range of 10–60 K. [ABSTRACT FROM AUTHOR]

The crystal structure, magnetic properties and magnetocaloric effect (MCE) of NdCo2-xMnx (x = 0.0–0.5) compounds have been investigated. X-ray diffraction (XRD) analysis has revealed that all the compounds crystallize in the MgCu2-type cubic Laves phase structure (C15-type, Fd-3m). The lattice parameter a increases from 7.2987 Ǻ (x = 0.0) to 7.4020 Ǻ (x = 0.5) and the Curie temperature from 102 to 202 K as the Mn content increases to x = 0.5. Under an external field change from 0 to 5 T, a maximum magnetic entropy changes (ΔSM) value of 8.75 J/kg K was obtained for NdCo2. With an increase of Mn content, the calculated ΔSM shows an obvious decrease with a broader peak. However, the relative refrigerating capacities (RCP) of the NdCo2–xMnx compounds are larger than the parent compound. The Arrott curves and universal curves of the rescaled ΔSM confirmed that the NdCo2–xMnx compounds undergo a second-order phase transition. [ABSTRACT FROM AUTHOR]

In this work, we have investigated the crystalline structure, martensitic transformation (MT) and magnetic properties of Co50V25-xNixGa25 (x = 5, 6, 7, 8, 9, 12.5) together with Co50V17Ni7Ga26 Heusler alloys. It was found that the MT behavior can occur in the Ni-doped Co50V25Ga25 Heusler alloys, and the MT temperature increases with the increase of Ni doping, which can reach about room temperature as the Ni doping increases up to x = 12.5. In the temperature interval of MT, with the decrease of temperature, the metamagnetic behavior appears from the ferromagnetic austenitic phase to the paramagnetic martensitic phase in the Co50V17Ni7Ga26 Heusler alloy. As a result, the magnetocaloric effect was observed, and the calculated magnetic entropy change can achieve about 11.5 J/kg K around 94 K for the magnetic field changes of 7 T. [ABSTRACT FROM AUTHOR]

In this research paper, a detailed investigation is conducted on the magnetocaloric effect (MCE) properties of the two phases (1−x) La0.6Ca0.4MnO3/(x) La0.6Sr0.4MnO3 composite system by experiments and numerical calculations. The polycrystalline manganites La0.6Ca0.4MnO3 and La0.6Sr0.4MnO3 are synthesized by the citric-gel method. Rietveld refinements of the X-ray diffraction patterns show that both samples are single phase. The Curie temperature Tc is found to be 255 and 365 K for La0.6Ca0.4MnO3 and La0.6Sr0.4MnO3, respectively. The study of the temperature dependence of the magnetic entropy change of (1−x)La0.6Ca0.4MnO3/(x)La0.6Sr0.4MnO3 composite indicates that the optimum composition stands for x = 0.6. Indeed, it gives comparable contributions of two parent compounds, leading to a practically uniform variation of entropy over a wide temperature range. The theoretical modeling of the MCE using Landau theory reveals an acceptable concordance with experimental data indicating the importance of magnetoelastic coupling and electron interaction in the MCE properties of manganite systems. [ABSTRACT FROM AUTHOR]

La0.7Ca0.3MnO3 perovskite and its composites with graphene nanoplatelet (GNP) were prepared using a wet chemical method. The structural, magnetic and magnetocaloric properties of La0.7Ca0.3MnO3: GNP composites were investigated to determine the effect of GNPs. The results of XRD analysis show that the synthesised powders can be almost indexed to pure phase orthorhombic La0.7Ca0.3MnO3. The magnetic measurements demonstrate that 0.7 and 1% GNP amounts cause an increase in the Curie temperature (TC), and for larger amounts of GNP, the TC monotonically decreases, except for the sample with 10% GNP. The results obtained from the Arrott plots show that the magnetic phase transition of the samples transforms from the first to second order with increasing GNP amount. The changes in the magnetocaloric properties are interpreted in terms of perovskite phase formations via structural analysis. The amounts of graphene nanoplatelets in the oxide powders are correlated with the observed magnetocaloric properties. The best magnetocaloric performance with the maximum magnetic entropy change of 3.99 Jkg−1K−1 and refrigeration capacity of 90 Jkg−1 was obtained at a 2 T magnetic field. [ABSTRACT FROM AUTHOR]

The effect of Zn content on magnetocaloric effect (MCE) in Pb(Zr0.52Ti0.48)O3–Ni(1−x)ZnxFe2O4 (PZT-NZF) with x = 0, 0.20, 0.30, 0.40 and 0.50 were investigated by phenomenological model. The results show that MCE for PZT-NZF is enhanced with low Zn content. However, for high Zn content samples, MCE for PZT-NZF decreases with Zn. In addition, MCE in PZT-NZF is tunable with Zn content and extends in highly temperature range. It is recommended that that MCE in PZT-NZF is beneficial for magnetic refrigeration for in high temperature. [ABSTRACT FROM AUTHOR]

The effect of Zn content on magnetocaloric effect (MCE) in Pb(Zr0.52Ti0.48)O3–Ni(1−x)ZnxFe2O4 (PZT-NZF) with x = 0, 0.20, 0.30, 0.40 and 0.50 were investigated by phenomenological model. The results show that MCE for PZT-NZF is enhanced with low Zn content. However, for high Zn content samples, MCE for PZT-NZF decreases with Zn. In addition, MCE in PZT-NZF is tunable with Zn content and extends in highly temperature range. It is recommended that that MCE in PZT-NZF is beneficial for magnetic refrigeration for in high temperature. [ABSTRACT FROM AUTHOR]

La0.8Ca0.2MnO3 manganese oxides have been prepared by the conventional solid-state reaction. The samples crystallize in the orthorhombic structure with Pnma space group. A first-order magnetic phase transition from ferromagnetic to paramagnetic state is observed at the Curie temperature that is found to be around 241 K. The magnetic and magnetocaloric properties have been simulated using a phenomenological model. The maximum of magnetic entropy change is of order 8.2 J/kg K for an applied magnetic field of 5 T, and the adiabatic temperature change is found to be of 4 K under a same magnetic field; this high value gives the sample the possibility of technologic application in the magnetic refrigeration area. The simulated results of magnetization and magnetic entropy change are compared with the experimental measurements. Finely, we found a good agreement between experimental and theoretical results. [ABSTRACT FROM AUTHOR]

La0.8Ca0.2MnO3 manganese oxides have been prepared by the conventional solid-state reaction. The samples crystallize in the orthorhombic structure with Pnma space group. A first-order magnetic phase transition from ferromagnetic to paramagnetic state is observed at the Curie temperature that is found to be around 241 K. The magnetic and magnetocaloric properties have been simulated using a phenomenological model. The maximum of magnetic entropy change is of order 8.2 J/kg K for an applied magnetic field of 5 T, and the adiabatic temperature change is found to be of 4 K under a same magnetic field; this high value gives the sample the possibility of technologic application in the magnetic refrigeration area. The simulated results of magnetization and magnetic entropy change are compared with the experimental measurements. Finely, we found a good agreement between experimental and theoretical results. [ABSTRACT FROM AUTHOR]

Three FeIII2LnIII2 tetranuclear heterometallic clusters, [H4LGd(H2O)Tp*Fe(CN)3]2·8H2O·2MeOH (1) and [H4LLn(MeOH)Tp*Fe(CN)3]2·6MeOH·2MeCN (Ln = Tb and Dy for 2 and 3, respectively, H6L = N,N′-(2,6-pyridine-dicarboxyl)-disalicylhydrazide, Tp* = hydridotris(3,5dimethylpyrazol-1-yl)-borate), were synthesized by use of the [(Tp*)Fe(CN)3]− unit as a metalloligand toward LnCl3 and H6L species. Structural analyses reveal that FeIII and LnIII ions in all complexes are connected to each other by one cyanide to form a heterobinuclear unit of [Ln(H4L)][(Tp*)Fe(CN)3], which is dimerized through Ln–N–C = O–Ln interaction. Magnetic susceptibility measurements show weak antiferromagnetic interactions between cyano-bridged FeIII and GdIII ions and amide-bridged GdIII ions are operative. Complex 1 displays the magnetocaloric effect with −ΔSmmax = 12.70 J·kg−1·K−1 at 4.0 K for ΔH = 7 T. No single-molecule magnetic properties are observed for 2 or 3 down to 1.8 K. [ABSTRACT FROM AUTHOR]

Ni48Mn39Sn13-xGex (x = 1, 2) Heusler alloys have been prepared, and the martensitic phase transition (MPT), magnetocaloric effect and exchange bias (EB) have been explored. At room temperature, the structure of both samples presents L21 type, and the MPT shifts to a higher temperature, while the Curie temperature (TC) of the austenitic phase decreases with the increase of the Ge content. The maximum magnetic entropy change of Ni48Mn39Sn13-xGex with x = 2 reaches about 14.67 J/kg K under the magnetic field of 5 T during reverse MPT. In addition, an interesting phenomenon is the enhancement of EB with the increase of the Ge content, especially the abnormal presence of the double-shifted hysteresis loop has been realized in Ni48Mn39Sn13-xGex with x = 2, which can be interpreted by the fact that the antiferromagnetic (AFM) regions couple with proximal ferromagnetic (FM) regions in the opposite way at low temperature. [ABSTRACT FROM AUTHOR]

In this study, the effect of Pb substitution with Sr on structural, magnetic and magnetocaloric properties in Pr(Sr1-xPbx)Mn2O6 (0.1 ≤ x ≤ 0.3) double perovskite manganite compounds prepared by the sol-gel method has been reported. Crystallinity has been worked by X-ray diffraction measurement and the Rietveld refinement method, which shows all samples are in monoclinic structure with P21/n space group without impurity phase. Scanning electron microscope analysis shows that all samples constituted from square-shaped grains with distinct grain boundaries, and energy-dispersive X-ray spectroscopy analysis shows that all expected elements are detected and there is no impurity element in the sample. All samples exhibit a magnetic phase transition from ferromagnetic to paramagnetic phase at TC determined as 274, 282 and 286 K for x = 0.1 (PSPM-1), 0.2 (PSPM-2) and 0.3 (PSPM-3) in the PrSr1-xPbxMn2O6 structure, respectively. Isothermal magnetisation curves near TC are used to determine the nature of the magnetic phase transition and the magnetic entropy change values (−ΔSM), which are found as 2.78, 3.11 and 3.52 J kg−1 K−1 for PSPM-1, PSPM-2 and PSPM-3 samples, respectively. Relative cooling power (RCP) values of the samples are also determined as 241, 311 and 246 J kg−1 for PSPM-1, PSPM-2 and PSPM-3 samples, respectively. ΔSM and RCP values are also calculated by using the Landau theory and the results are in accordance with the experimental results, which indicate the role of electron condensation energy and magneto-elastic coupling in magnetic entropy change value of the samples. [ABSTRACT FROM AUTHOR]

The effect of heat treatment on the structural, magnetic and magnetocaloric properties of Ni43Mn46In11 melt-spun ribbons was systematically investigated using X-ray powder diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), magnetic force microscope (MFM) and magnetic measurements. From the XRD studies, tetragonal and cubic phases were detected at room temperature for as-spun, quenched and slow-cooled ribbons. Furthermore, it was observed, upon annealing martensite transition temperatures increased when compared to the as-spun ribbon. To avoid magnetic hysteresis losses in the vicinity of the structural transition region, the magnetic entropy changes-ΔS m of the investigated ribbons were evaluated from temperature-dependent magnetisation-M(T) curves on cooling for different applied magnetic fields. The maximum ΔS m value was found to be 6.79 J kg−1 K−1 for the quenched ribbon in the vicinity of structural transition region for a magnetic field change of 50 kOe. [ABSTRACT FROM AUTHOR]

In dendrimer complexes of iron (III) with Schiff base (three complexes of iron (III) based on azomethine 4,4′-dodecyloxybenzoyloxybenzoyl-4-salicylidene-2-aminopyridine, a significant magnetocaloric effect (MCE) and heat capacity was found the first time. It was found that the magnitude of MCE depends on the nature of the counter-ion of the complex. MCE were measured with a microcalorimeter over the temperature range of 278-320 K and in a magnetic induction of 0-1.0 T. The temperature dependences of the MCE dendrimer complexes of iron (III) with Schiff base were obtained for the first time. For all the samples studied, the existence of extreme temperature dependence of MCE in the range of temperatures 300-350 K, which is possibly the result of the magnetic phase transition, is shown. The correlation between the thermotropic mesomorphism with the magnetic phase transition in complexes has been established. [ABSTRACT FROM AUTHOR]

The magnetic properties and magnetocaloric effect in YMnO3 have been investigated using Monte Carlo simulations. The thermal magnetization, specific heat and magnetic entropy have been obtained for different values of exchange interactions and for a several external magnetic field values. The variation of adiabatic temperature change with the temperatures has been obtained for several values of external magnetic field. It has been found that the sample exhibited a paramagnetic to ferromagnetic phase transition at 30 K. The transition temperature of YMnO3 has been deduced for different values of size (1/L) and different values of exchange interactions. The relative cooling power with several values of external magnetic field has been established. [ABSTRACT FROM AUTHOR]

In this paper, a table-like magnetocaloric effect (MCE) is obtained in the (AMn0.9Ti0.1O3)1−x/(AMn0.85Ti0.15O3)xcomposite system. A flattening behaviour of the entropy change is investigated from the isothermal magnetic entropy change versus temperature curves ∆S(T) of AMn0.9Ti0.1O3and AMn0.85Ti0.15O3(A = La0.57Nd0.1Pb0.33) manganite materials. Both compounds exhibit nearly some large MCE, 5.2–4.85 J kg−1K−1, under an applied field of 0–5 T, around their respective Curie temperature (TC) ranged from 279 to 299 K. The temperature dependence of the isothermal magnetic entropy change ΔS(T) is calculated for (AMn0.9Ti0.1O3)1−x/(AMn0.85Ti0.15O3)xcomposite with 0 ≤x≤ 1. The optimum ΔS(T) of the composite withx= 0.495 approaches a nearly constant value of ∼3.63 J kg−1K−1in a field change of 0–5 T in a wide temperature span over 15 K, resulting in large refrigerant capacity value of ∼172.3 J kg−1. The (AMn0.9Ti0.1O3)0.505/(AMn0.85Ti0.15O3)0.495composite system indicates that this approach can be used to design magnetic refrigerant materials with enhanced magnetocaloric response in a magnetic refrigerator performing an Ericsson cycle near room temperature. [ABSTRACT FROM AUTHOR]

The impacts of adding Cr on the Curie temperature (TC), glass-forming ability (GFA), and magnetocaloric effect were studied in Fe68−xCrxTb5B23Nb4(x = 0, 2, 4, 6 and 8) metallic glasses prepared by suction casting. GFA depends on Cr content in the composition. For Fe68−xCrxTb5B23Nb4bulk metallic glasses (BMGs), with critical diameters up to ~3 mm can be produced by suction casting and maximum value of GFA was found forx = 6. By exchanging Cr with Fe partially,TCcould effectively be adjusted in a quite broad temperature interval from 487 K forx = 0 to 267 K forx = 8, whereas maximum magnetic entropy change decreased from 1.16 to 0.53 Jkg−1 K−1and refrigeration capacity (RC) changed from 116 to 45.05 J/kg under a low field change of 2 T. ThoughTCis shifted to room temperature, maximum magnetic entropy change and RC decreased almost half of the base alloy. To enhance these properties (Fe0.62Cr0.06Tb0.05B0.23Nb0.04)100−yCuy(y = 0.75, 1), metallic glasses are prepared. By the help of small addition of Cu, magnetocaloric properties can be effectively increased without changing theTC. These findings show that the successful synthesis of the Fe-based Fe62Cr6Tb5B23Nb4and (Fe0.62Cr0.06Tb0.05B0.23Nb0.04)100−yCuy(y = 0.75, 1) BMGs near room temperature, could be considered as promising candidates as magnetic refrigerant materials. [ABSTRACT FROM AUTHOR]

In this work, we have studied on double-layered perovskite (Ruddlesden–Popper) manganite structure in Pr1.75Sr1.25Mn2O7synthesised by sol–gel method. The crystal structure of the double-layered perovskite is found as tetragonal from the X-ray diffraction analysis with I4/mmm space group. A high Curie temperature,TC = 305 K is observed from the temperature dependence of magnetisation measurement. The isothermal magnetisation curves showed that magnetic phase transition is second order due to the positive slope of the Arrott plots. Maximum magnetic entropy change (ΔSM) and adiabatic temperature change (ΔTad) values are calculated as 3.99 J kg−1K−1and 2.1 K under external magnetic field of 70 kOe, respectively. Since our double-layered perovskite manganite sample has desiredTCvalue and relatively high ΔSM, it can be a potential candidate as a magnetocaloric material for room temperature magnetic cooling systems. [ABSTRACT FROM PUBLISHER]

The present work is devoted to a review of the phenomenological model proposed by Mahmoud Aly Hamad (M. Aly Hamad, Phase Transitions 85 (2012) 106–112) to predict the magnetocaloric effect in ferromagnetic material from the only measure of its magnetization as a function of temperature under an applied magnetic field. We questioned the reliability of that model. Based on some experimental data available in the literature, we have shown that, contrary to what is expected, the prediction of the magnetocaloric effect by this model is poor. [ABSTRACT FROM AUTHOR]

The magnetocaloric and magnetoresistance properties of amorphous Co-based (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)100−xCux(x = 0, 0.5, 0.75 and 1) ribbons were investigated. Cu additions changed the crystallisation temperature (Tx) and the Curie temperature (TC). The saturation magnetisation (Ms) and coercivity (Hc) for alloys were in the range of 65.51–38.49 emu/g and 1.99–6.84 A/m, respectively. Under an applied magnetic field change of 2.2T, the (−ΔSM)maxfor (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)100−xCuxwithx = 0, 0.5, 0.75 and 1 are 0.77, 0.71, 0.89 and 0.67 Jkg−1 K−1, respectively. The values of refrigeration capacity (RC) for the as-spun glassy alloys are comparable with those of previously studied Fe-based metallic glasses such as Fe80B10Zr9Cu1, (Fe0.76B0.24)96Nb4and Fe82Ni2Zr6B10. In addition, the maximum magnetoresistance (MR) values for (Co0.402Fe0.201Ni0.067B0.227Si0.053Nb0.05)100−xCuxwithx = 0, 0.5, 0.75 and 1 are found to be 110, 38, 23 and 1% around the Curie temperatures under an applied magnetic field change of 1T, respectively. With good RC, negligible hysteresis due to very low coercivity values and large magnetoresistance, these Co-based amorphous alloys can be used as the high temperature magnetic refrigerants and multifunctional applications working in the temperature range of 450–600 K. [ABSTRACT FROM PUBLISHER]

With increasing amount of nickel in the Gd7Pd3-xNixseries, the unit cell volume decreases due to difference between atomic radius of Pd and Ni but the type of crystal structure is preserved. The paper presents X-ray diffraction, Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometer, Transmission Electron Microscopy, AC and DC magnetic susceptibility and magnetocaloric examinations of the series. The Ni substitution into Pd position causes the decrease in the Curie temperature. Moreover, the dispersion observed in the AC-susceptibility at different frequencies vanishes at the Curie point. Just below the ordering temperature, a Hopkinson peak is observed. Complex processes depending on frequency and magnetic field occur in the transition region. The magnetization phenomena are very sensitive to the applied DC magnetic field and even very weak fields producing thermomagnetic hysteresis. A reorientation process around 150 K exists in all compounds and it is connected with increasing interactions at low temperatures. After nickel substitution, the relative cooling power (RCP) is greater in comparison to the parent compound. [ABSTRACT FROM AUTHOR]

We report on the effect of Pr doping on structural, magnetic and magnetocaloric properties in (La1?xPrx)0.85Ag0.15MnO3(0.0 ? x ? 0.5) compounds. The main crystal structure has been studied by performing X-ray diffraction method and structural analysis based on Rietveld method where it is found that although samples at low concentration level (x ? 0.2) have rhombohedral phase, others (x ? 0.3) have orthorhombic (Pbnm) phase. Scanning electron microscope images show that the average particle size decreases by increasing Pr amount in the main structure. It is observed that the second-order transition temperature from ferromagnetic to paramagnetic phase is dramatically decreased from 262 to 138 K by increasing Pr concentration in (La1?xPrx)0.85Ag0.15MnO3. On the other hand, all samples have also antiferromagnetic coupling observed belowTN ~ 50 K. The maximum magnetic entropy change (??SM)maxand relative cooling power values were found in the range of 7.90–2.88 J/kg K and 213.32–153.50 J/kg, respectively, under 50 kOe field change in our samples. It can be argued that particularly the compounds LPAM withx = 0.0, 0.1 and 0.2 are expected to be promising candidate for magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Heat transfer, thermal management, and acoustics are the important parameters that determine the effectiveness of any miniaturized electronic circuit. As the density of electronic components is increasing, the reliability of such systems is of great concern. The proposed work discusses a novel technique of a magnetic pumping fluid system without conventional cooling components. Here the integrated effect of the conjugate heat transfer and magnetic field is taken into account to study flow phenomena. Two different fluids—water and kerosene—as a base fluid for ferrofluid are evaluated for physical quantities such as pressure, temperature, and heat transfer coefficient to measure the performance of a magnetic cooling system. Flow in the cooling setup is optimized by using numerical analysis and number of experiments on the given setup. It was found that flow depends on the magnetic field gradient, temperature gradient, fluid properties, and material combination. In addition, flow characteristics depend on the influence of magnetic field and temperature of the fluid. Analysis results show that the heat transfer and pressure head in the kerosene-based ferrofluid are more stable compared to the water-based ferrofluid. A better magnetic fluid with both high magnetization and a high pyromagnetic coefficient can enhance the flowability of the ferrofluid to a large extent. [ABSTRACT FROM PUBLISHER]

A compilation of magnetocaloric properties of metallic nanostructures with Curie temperature (TC) between 260 and 340 K has been tabulated. The tabulated data show that nanostructure plays an important role in enhancing the magnetocaloric properties of a material, namely by reducing the peak of magnetic entropy, but broadening of the magnetocaloric effect curve with an average of 10 K sliding window for Curie temperature. A second table lists all bulk metallic and intermetallic materials, in which there is no nanostructural data, with an entropy change of at least 20 J/kg K and a Curie temperature between 260 and 340 K. We propose that further experiments should be made on the nanostructured form of these materials. [ABSTRACT FROM AUTHOR]

The critical exponents of second-order phase transition were deduced from magnetic entropy change. Using the magnetic field dependence of entropy change and the Widom scaling relation, some relevant critical exponents can be calculated directly from them. Based on critical exponents, a corresponding Arrott plot can be established as an initial model. Through a limited nonlinear fitting, we can obtain the final critical exponents. This method eliminates the drawbacks of the routine method which relies on the subjective selection of an initial model and involves the multi-step nonlinear fitting process. It was applied to the manganite NdSrCaMnOto verify its utility and feasibility. The spontaneous magnetization obtained using the final critical exponents is consistent with that deduced from the isothermal magnetization measurements, indicating that the utilization of the magnetic field dependence of magnetic entropy change to determine critical exponents is a valid method. [ABSTRACT FROM AUTHOR]

The magnetocaloric properties for the Eu-doped La0.65−xEuxSr0.35MnO3samples withx= 0.05, 0.15, 0.20, and 0.30 upon 0.05T magnetic field have been investigated. It is found that the Eu doping in this system decreases the magnetocaloric properties lightly. Moreover, the results of Eu doping clearly indicate that the magnetocaloric effect in this system is tunable, which is beneficial for manipulating magnetocaloric refrigeration that occurs in various temperature ranges. This makes the La0.65−xEuxSr0.35MnO3samples potential candidates for practical applications. A complete characterization of the magnetic properties of this material aids to the understanding required for the technological exploitation of such materials, and it suggests La0.65−xEuxSr0.35MnO3perovskite as the promising magnetic refrigerant. [ABSTRACT FROM AUTHOR]

The magnetocaloric effect (MCE) has been measured by direct method in La0.8Ag0.15MnO3and La0.85Ag0.15MnO3before and after coating of Fe–Co layer on the surfaces of manganites. An evaporated film thickness has been 500 nm. The measurements have shown the MCE to be increased by 7%–8% under 26 kOe after Fe–Co coating on the flat surfaces. [ABSTRACT FROM AUTHOR]

Ni39+xMn50Sn11-x (x = 0.5, 1.0, 1.5 and 2) alloys comprise multiple martensite nanostrips of nanocrystallites when cast in small discs, for example, ∼15mm diameter and 8mm width. A single martensite phase with a L10 tetragonal crystal structure at room temperature can be formed at a critical Sn content of 9.0 at.% (x = 2), whereas an austenite cubic L21 phase turns up at smaller x ≤ 1.5. The decrease in the Sn content from x = 2 to 0.5 also results in a gradual increase in the crystallite size from 11 to 17 nm. Scanning electron microscopy images reveal arrays of regularly displaced multiple martensite strips (x ≥ 1.5) with an average thickness of 20 nm. As forced oscillators, these strips carry over the local strains, magnetic dipoles, and thermions simultaneously in a martensite-austenite (or reverse) phase transition. A net residual enthalpy change ΔHM↔A = -0.12 J g-1 arises in the process that lacks reversibility between the cooling and heating cycles. A large magnetoresistance of (-)26% at 10 T is observed together with a large entropy change of 11.8 mJ g-1 K-1, nearly twice the value ever reported in such alloys, in the isothermal magnetization at 311 K. The ΔHM↔A irreversibility accounts for a thermal hysteresis in the electrical resistivity. Strain induced in the martensite strips leads them to have a higher electrical resistivity than that of the higher-temperature austenite phase. A model considering time-dependent enthalpy relaxation explains the irreversibility features [ABSTRACT FROM AUTHOR]

The dependence of magnetization on the variation of temperature for La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3 perovskite-type ceramic materials under an external magnetic field was modelled. Application of phenomenological model was performed, showing a good agreement with the experimental data. Temperature dependence of change of both magnetic entropy and specific heat under magnetic field 0.05 T was predicted for La0.67Ca0.33MnO3 and La0.67Sr0.33MnO3. Predicted values of maximum magnetic entropy change, full-width at half-maximum, relative cooling power and maximum specific heat under 0.05 T were evaluated. [ABSTRACT FROM PUBLISHER]

The specific heat and magnetocaloric effect (MCE) of A-site ordered PrBaMn2O6 manganite have been studied. The anomalies caused by the ferromagnetic (FM) and antiferromagnetic (AFM) phase transitions are revealed in the specific heat curve. Direct and inverse MCE are observed at the Curie and Neel points correspondingly. A value of the inverse MCE in the heating run is smaller than in the cooling regime. We attribute this effect to the competition between FM and AFM interactions. A significant advantage of PrBaMn2O6 as a magnetocaloric material is an MCE spanning a broad range of temperature with a maximum at room temperature. [ABSTRACT FROM AUTHOR]

The magnetocaloric effects (MCEs) in cubic NaZn13-type La(FexSi1−x)13 compounds and their hydrides composed of icosahedral clusters have been investigated because these compounds exhibit the itinerant-electron metamagnetic (IEM) transition just above the Curie temperature TC. The value of TC can be increased continuously up to about 336 K by hydrogen absorption into the La(FexSi1−x)13 compounds. Therefore, the values of the isothermal magnetic entropy change ΔSm and the indirectly estimated adiabatic temperature change ΔTad due to the IEM transition become −31 J/kg K and 15.4 K, respectively, in the magnetic field change from 0 to 5 T at TC=287 K for the La(Fe0.90Si0.10)13H1.1 compound. The MCEs in the compounds having the IEM transition are much larger than those in the compounds exhibiting the second-order magnetic transition at TC. The direct measurement of the adiabatic temperature change ΔTadd has confirmed such a large value. Consequently, the La(FexSi1−x)13 compounds and their hydrides having the IEM transition are promising as high performance magnetic refrigerants working in a wide temperature range covering room temperature in relatively low magnetic fields. [Copyright &y& Elsevier]

The rate-independent stabilization of magnetic states with iterations in a Heusler alloy has been studied. The direct measurement of the adiabatic temperature change, ΔTad, of a Ni51Mn33.4In15.6alloy near the magnetostructural phase transition is presented. The adiabatic temperature change at a given temperature within the temperature range of the magnetostructural transition is history dependent and varies considerably with the iteration count of the field cycle. The data show the transition from the low magnetization state to the high magnetization state during low to high (L–H) temperature change direction and from high magnetization to low magnetization state during high to low (H–L) temperature change direction require several field cycles to stabilize the ΔTadmeasurement, similar to the accommodation phenomenon in hysteretic materials. In the mixed magnetic state inside the first-order transition, both low and high magnetization portions of the alloy exist and it varies considerably with the induced fields. This original observation emphasizes that it is incorrect to assess the performance of a magnetic refrigeration system through a single measurement, and that achieving a stable, utilizable, adiabatic temperature change requires several field-induced transitions. [ABSTRACT FROM AUTHOR]