Large Magnetic Entropy Change Research Articles

Composition Dependence of Magnetocaloric Effect in Pr<SUB>0.6</SUB>Ca<SUB>0.4</SUB>Mn<SUB>1−<I>x</I></SUB>Cr<SUB><I>x</I></SUB>O<SUB>3</SUB> (<I>x</I> = 0.02–0.08)

We report the effect of varying Cr content on magnetic and magnetocaloric properties of Pr0.6Ca0.4Mn(1-x)Cr(x)O3 samples (x = 0, 0.02, 0.04, 0.06 and 0.08). While the parent compound (x = 0) is a charge ordered and antiferromagnetic insulator, Cr doped compounds are ferromagnetic metals with nearly same Curie temperature (T(c) approximately 140 K). We find unusual field-induced meta-magnetic transition above T(c) in x = 0.02 and 0.04 which is absent in x = 0.06 and 0.08. It is suggested that the paramagnetic phase in these compounds is inhomogeneous with coexistence of nano-size ferromagnetic clusters and short range charge ordered clusters. Field induced growth of ferromagnetic nano-clusters and destruction of short-range charge ordering leads to the observed metamagnetic transition, which results in large magnetic entropy change of -deltaS(M) = 5.043, 6, 5.509 and 4.375 J/kg K under deltaH = 5 T, for x = 0.02, 0.04, 0.06 and 0.08, respectively. In addition, large relative cooling power (RCP) found in these materials (327.384, 286.36, 272.22 and 279.936 J/kg) makes it interesting for practical applications. Our study suggests that creation of ferromagnetic nano-clusters in the paramagnetic phase by Mn-site doping in charge ordered compounds provides an alternative approach to achieve high AS(M) and RCP values.

Effect of Al substitution on magnetocaloric effect in La0.57Nd0.1Sr0.33Mn1−xAlxO3 (0.0 ≤ x ≤ 0.30) polycrystalline near room temperature

We have investigated the effect of aluminum (Al) doping on the magnetic and magnetocaloric properties of La0.57Nd0.1Sr0.33Mn1−xAlxO3 (LNSMAO) (0.0≤x≤0.3). The Curie temperature TC of the prepared samples is found to be strongly dependent on the aluminum content and it spans between 238K and 342K. It has been analyzed by using two methods: a linear extrapolation of M (T) to zero magnetization and the thermodynamic model. With an increasing Al concentration, a systematic increase in the values of magnetic entropy is observed. The magnitude of the isothermal magnetic entropy (ΔSM) at the FM Curie temperature increases from 2.31J/kgK for x=0 to a maximum value of 3.58J/kgK for x=0.3 for a magnetic field change of 10kOe. Moreover, the relative cooling power (RCP) increases from 23J/kg to 68J/kg, respectively. Large magnetic entropy changes upon the application of a low magnetic field and a wide temperature range of TC suggest that these materials can be used as candidates for magnetic refrigerants.

Magnetocaloric effect and its implementation in critical behavior study of Mn4FeGe3−xSix intermetallic compounds

Magnetocaloric effect in Mn4FeGe3−xSix compounds has been studied by dc magnetization measurements. For the parent compound Mn4FeGe3, the paramagnetic to ferromagnetic transition temperature TC is above room temperature (320 K), which initially remains constant for small Si substitution at the Ge site and then decreases marginally with an increase in Si concentration. A large change in magnetic entropy at the TC, under a magnetic field variation of 50 kOe, with typical values of 5.9, 6.5, 5.9, and 4.4 J kg−1 K−1for x = 0, 0.2, 0.6, and 1 samples, respectively, along with a broad operating temperature range and a negligible hysteresis make Mn4FeGe3−xSix series a promising candidate for magnetic refrigerant material around room temperature. Mn4FeGe3−xSix series is found to undergo a second-order magnetic phase transition. The field dependence of the magnetic entropy change has been brought out and implemented to deduce the critical exponents. The critical behavior study shows that the magnetic interactions for x = 0 and 0.2 samples have two different behaviors below and above TC. Below TC, it follows the mean field theory with long-range magnetic interaction and above TC it follows the Heisenberg three-dimensional model with short-range or local magnetic interaction. The magnetic exchange interactions for the x = 0.6 and 1 samples follow the mean-field theory.

Local structure and magnetocaloric effect for La0.7Sr0.3Mn1−xNixO3

We have prepared polycrystalline La0.7Sr0.3Mn1−xNixO3 (x = 0, 0.01, 0.02, 0.03) samples by conventional solid-state reaction. X-ray absorption studies reveal that Ni dopants in the compounds having an oxidation state of 2+. These Ni2+ ions replace Mn on the octahedral site of the perovskite structure. An increase of the Ni content enhances the concentration of Mn4+ ions. This reduces magnetization, and the ferromagnetic-paramagnetic phase transition temperature (TC) of La0.7Sr0.3Mn1−xNixO3 from ∼365 K for x = 0 to ∼345 K for x = 0.03. The magnetocaloric effect has also been assessed by means of magnetic-entropy change, which is determined from field dependences of magnetization. We find a large magnetic-entropy change taking place around TC of the samples. Under an applied field interval of 15 kOe, the maximum magnetic-entropy changes |ΔSMmax| are about 2.33, 2.27, 2.26 and 2.21 J/kg K for x = 0, 0.01, 0.02, and 0.03, respectively. Interestingly, the doping of a small amount of Ni in La0.7Sr0.3Mn1−xNixO3 does not make|ΔSMmax| changed very much, but causes the shift of this value towards room temperature. Such the feature is applicable to control the working temperature range of cooling systems based on the magnetocaloric effect.

Phase diagram and magnetocaloric effect in Mn 2Ni 1.64−xCo xSn 0.36 alloys

The effect of Co substitution for Ni in Mn-rich Mn2Ni1.64−xCoxSn0.36 ferromagnetic shape memory alloys has been studied. With increasing Co content, the martensitic transformation temperatures decrease due to the decrease in valence electron concentration. The great enhancements of magnetization and Curie temperature by Co doping could be attributed to the strong Co–Mn interaction, changing Mn–Mn coupling from antiferromagnetic to ferromagnetic. In the composition range of 0.08⩽x⩽0.24, large magnetization changes and large magnetic entropy changes are observed with martensitic transformation.

Magnetocaloric effect contributed by in situ dual-phase structure in the Gd-Co-Al alloy

In many cases, the presence of secondary phase will deteriorate the magnetocaloric effect of materials due to the difference in magnetic properties. However, the alloy with in situ dual-phase structure and good magnetocaloric effect was found in the pseudo-binary GdCo2-GdAl2 system. Experiments revealed that the GdCo0.65Al1.35 alloy comprised the primary terminal GdAl2 phase and the secondary intermediate GdCo0.74Al1.26 phase. Both of them ordered at 70 K simultaneously. Large magnetic entropy change and relative cooling power of 11.0 J/kg K and 638 J/kg for 0–50 kOe field changes, respectively, were obtained due to the contribution of both GdAl2 and GdCo0.74Al1.26 phases.

Large reversible magnetocaloric effect in HoTiO3 single crystal

Large magnetocaloric effect has been observed in perovskite-type HoTiO3 single crystal accompanied by a second-order magnetic phase transition at TC ≈ 53 K. The values of maximum magnetic entropy change are about 5.96 and 11.56 J kg−1 K−1 under the magnetic field change of 2 and 5 T, respectively, without any detectable thermal and magnetic hysteresis loss. The large magnetic entropy change is attributed to the sharp magnetization jump, related to anomalies of the lattice parameters just at the Curie temperature. Such a large reversible magnetocaloric effect makes the perovskite HoTiO3 attractive for pursuing new materials for magnetic refrigeration.

Influence of H and Extra La on Magnetocaloric Effect of La$_{0.5 + x}$Pr$_{0.5}$Fe$_{11.4}$Si$_{1.6}$ Melt-Spun Ribbons

Magnetic properties and magnetocaloric effect were investigated on La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5+x</sub> Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11.4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> =0, 0.1, 0.2) melt-spun ribbons. It was found that NaZn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13</sub> -type phase could be obtained easily owing to that the segregation of α-Fe phase was suppressed obviously by adding appropriate amount of La after a short time annealing for melt-spun ribbons. For the La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11.4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> ribbons, the Curie temperature was adjusted dramatically from low temperature of 193 K to room temperature of 321 K due to the interstitial hydrogen adsorption. With La content increasing, Curie temperature was slightly increased; the magnetic hysteresis was reduced, while a large magnetic entropy change remained. The maximum magnetic entropy change (- Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SM</i> ) is 33.8 J/(kg·K) for La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11.4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> while that of La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11.4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> is 19.6 J/(kg·K) in a magnetic field change of 5 T. It is shown that rapid quenching to make LaFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13-x</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> alloys is more cost effective than arc melting method by reducing annealing time substantially. High magnetic entropy change and low magnetic hysteresis were obtained by adding extra La and the Curie temperature was tuned to near room temperature by interstitial atom H. This work indicated that La <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> Pr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.5</sub> Fe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11.4</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1.6</sub> H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> was a promising magnetic refrigeration material near room temperature.

Large reversible magnetocaloric effect in spinel MnV2O4 with minimal Al substitution

Magnetocaloric effect of MnV1.95Al0.05O4 was studied by the magnetization and heat capacity measurements. MnV1.95Al0.05O4 is a cubic spinel structure with ferromagnetism of second order in nature and performs reversible magnetic entropy around the magnetic transition temperature. The large magnetic entropy changes −ΔSM∼5.2 and 8.2J/kgK and the adiabatic temperature changes ΔTad∼1.5 and 2.6K are revealed for the magnetic field changes of 2 and 4T near the Curie temperature (TC) of 59.6K, respectively. The relative cooling power (RCP) are about 82.2 and 177.2J/kg K for magnetic field changes 2 and 4T, respectively. Compared with the parent compound, although the −ΔSM and ΔTad become smaller, the refrigeration working temperature span and the RCP have been improved.

Magnetic and magnetocaloric properties of Pr 0.6− xEu xSr 0.4MnO 3 manganese oxides

Studies of the structural, magnetic and magnetocaloric properties of polycrystalline Pr 0.6− x Eu x Sr 0.4MnO 3 (0≤x≤0.15) perovskite manganites were carried out. Substitution for praseodymium with europium, with smaller ionic radius, induces local distortion in the 〈Mn–O–Mn〉 bonds and consequently causes a random distribution in the magnetic exchange interactions. The competition between magnetic interactions leads to the appearance of an inhomogeneous magnetic state in our samples. Pr 0.6− x Eu x Sr 0.4MnO 3 ( x = 0 , 0.05, 0.1 and 0.15) polycrystalline samples were prepared using the solid–solid reaction method at high temperature. The compounds yielded are single phase and crystallize in the orthorhombic system with the Pnma space group. The substitution of Eu for Pr leads to a decrease of the Curie temperature T C from 303 K for x = 0.00 to 260 K for x = 0.15 . All of our compounds exhibit a large magnetic entropy change with a maximum around 2.2 J/kg K under a magnetic applied field change of 2 T for all compounds.

Kinetic study on the non-isothermal crystallization of Gd 53Al 24Co 20Zr 3 bulk metallic glass

Gd-based bulk metallic glass has drawn strong attention because of its large magnetic entropy changes. Thermal stability of metallic glass is a very important issue for its application. In the paper, crystallization behavior of Gd 53Al 24Co 20Zr 3 bulk metallic glass was investigated using non-isothermal differential scanning calorimetric (DSC) technique. Attention was given to the analytic details. The crystallized volume fractions as a function of temperature were derived from the DSC signals, where heat capacity change between amorphous phase and crystalline phase was considered. The local activation energies at different crystallized volume fraction were estimated using Doyle-Ozawa and Agrawal methods. The results suggested that the Doyle-Ozawa equation was appropriate to get local activation energy due to its simplicity and accuracy. The local activation energy depended on the crystallized volume fraction. Function reflecting crystallization mechanism was also deduced. The crystallization mechanism of the Gd-based bulk metallic glass was discussed.

Effects of the Mn/Co ratio on the magnetic transition and magnetocaloric properties of Mn1+xCo1−xGe alloys

We have investigated the magnetic transition and magnetocaloric effects of Mn1+xCo1−xGe alloys by tuning the ratio of Mn/Co. With increasing Mn content, a series of first-order magnetostructural transitions from ferromagnetic to paramagnetic states with large changes of magnetization are observed at room temperature. Further increasing the content of Mn (x = 0.11) gives rise to a single second-order magnetic transition. Interestingly, large low-field magnetic entropy changes with almost zero magnetic hysteresis are observed in these alloys. The effects of Mn/Co ratio on magnetic transition and magnetocaloric effects are discussed in this paper.

Magnetocaloric effect in composite structures based on ferromagnetic–ferroelectric Pr 0.6Sr 0.4MnO 3/BaTiO 3 perovskites

We have prepared composite materials composed of ferromagnetic and ferroelectric compounds having the general formula (1 − x)(Pr 0.6Sr 0.4MnO 3)/ x(BaTiO 3), with x is the molar ratio ( x = 0.0, 0.03, 0.05, 0.10 and 0.30) using conventional ceramic double sintering process. We report the structural, magnetic and magnetocaloric properties of all samples. The presence of the two phases of Pr 0.6Sr 0.4MnO 3 (PSMO) and BaTiO 3 (BTO) was confirmed by X-ray diffraction (XRD) technique and the structural analysis. Magnetic measurements of magnetization versus temperature and magnetic applied field were performed. The temperature dependence of magnetization reveals that the composite samples show paramagnetic to ferromagnetic phase transition (PM–FM) when the temperature decreases. These samples have the same Curie temperature as the parent PSMO compound ( T c ≈ 273 K). The magnetic entropy change |Δ S M | was deduced from the M( H) data by the Maxwell relation. Close to T c , a large change in magnetic entropy has been observed in all samples. The maximum value of the magnetic entropy | Δ S M max | decreases from 2.88 J kg −1 K −1 for x = 0–1.86 J kg −1 K −1 for x = 0.3 for an applied magnetic field of 2 T. At this value of magnetic field the relative cooling power (RCP) decreases equally from 63 J kg −1 for the parent sample to 38.3 J kg −1 for x = 0.3. The temperature dependence of the Landau coefficients has been deduced using the Landau expansion of the magnetic free energy, indicating the second order nature of the magnetic transition.

Structure, magneto-structural transitions and magnetocaloric properties in Ni50−xMn37+xIn13 melt spun ribbons

Melt spun Ni50−xMn37+xIn13 (2≤x≤5) ribbons were investigated for the structure, microstructure, magneto-structural transitions and inverse magnetocaloric effect (IMCE) associated with the first-order martensitic phase transition. The influence of excess Mn in Ni site (or Ni/Mn content) on the martensite transition and the associated magnetic and magnetocaloric properties are discussed. It was found that with the increase in Mn content, the martensitic transition shifted from 325 to 240K as x is varied from 2 to 4, and the austenite phase was stabilized at room temperature. The x=5 ribbon did not show the martensitic transition. For the x=3 ribbon, the structural and magnetic transitions are close together unlike in the x=4 ribbon in which they are far (∼60K) apart. The zero field cooled and field cooled curves support the presence of exchange bias blocking temperature due to antiferromagnetic interactions in the ribbons. A large change in the magnetization between the martensite and austenite phases was observed for a small variation in the Ni/Mn content, which resulted in large IMCE. A large positive magnetic entropy change (ΔSM) of 32J/kgK at room temperature (∼ 300K) for a field change of 5T with a net refrigeration capacity of 64J/kg was obtained in the Ni47Mn40In13 ribbon.

Giant anisotropy of magnetocaloric effect in TbMnO3single crystals

The magnetocaloric effect (MCE) in TbMnO${}_{3}$ single crystals was investigated by isothermal magnetization curves for the $\mathit{ab}$ plane at low temperatures. Large magnetic entropy change, $\ensuremath{\Delta}{S}_{M}$ $=$ \ensuremath{-}18.0 J/kg K, and the refrigerant capacity, RC $=$ 390.7 J/kg, are achieved near the ordering temperature of Tb${}^{3+}$ moment (${T}_{N}^{\mathrm{Tb}}$) under 70 kOe along the $a$ axis. Furthermore, the TbMnO${}_{3}$ single crystal exhibits a giant MCE anisotropy. The difference of $\ensuremath{\Delta}{S}_{M}$and RC between the $a$ and $b$ axes is field and temperature dependent, which reaches maximum values of 11.4 J/kg K and 304.1 J/kg, respectively. By taking magnetocrystalline anisotropy into account, the rotating $\ensuremath{\Delta}{S}_{M}$within the $\mathit{ab}$ plane can be well simulated, indicating that the anisotropy of $\ensuremath{\Delta}{S}_{M}$is directly contributed from the magnetocrystalline anisotropy. Our finding for giant MCE anisotropy in TbMnO${}_{3}$ single crystals explores the possibility of using this material for magnetic refrigerators by rotating its magnetization vector rather than moving it in and out of the magnet.

Magnetism and magnetocaloric properties of Mn 0.95Cr 0.05As

In this study the magnetic properties of Mn 0.95Cr 0.05As, prepared by mechanical milling, have been investigated. The results suggest that the presence of strains is very important for the magnetic state of the compound. In the presently studied compound, a combined magnetic and structural transition occurs from paramagnetic MnP phase to ferromagnetic NiAs phase at about 234 K. With further decreasing temperature, at 159 K, a transition from ferromagnetic NiAs phase to helimagnetic (H a -type) MnP phase is observed, which is accompanied by an inverse magnetocaloric effect. The ferromagnetic phase is recovered when the temperature is increased. At both first-order transitions, at 159 and 234 K, large magnetic-entropy changes are observed.

Magnetic properties and large magnetocaloric effect in Gd–Ni amorphous ribbons for magnetic refrigeration applications in intermediate temperature range

Amorphous Gd 68− x Ni 32+ x ( x = −3, 0, 3) ribbons were prepared by melt-spinning method. The crystallization onset temperatures T x1 for Gd 68− x Ni 32+ x amorphous ribbons with x = −3, 0, and 3 are 561, 568, and 562 K, respectively. All the samples undergo the second-order magnetic transition at temperatures between ∼122 ( x = −3 and 3) and 124 K ( x = 0). The Curie temperature T C does not change with the composition significantly. The maximum isothermal magnetic entropy changes (−Δ S M) max of Gd 71Ni 29, Gd 68Ni 32, and Gd 65Ni 35 amorphous ribbons for a magnetic field change of 0–5 T were 9.0, 8.0, and 6.9 J kg −1 K −1, respectively. Large values of the refrigerant capacity (RC) were obtained in these ribbons. For example, Gd 71Ni 29 amorphous ribbon has a maximum RC value of 724 J kg −1. Large magnetic entropy change and RC values together with high stability enable the Gd 71Ni 29 amorphous alloy a competitive candidate among the magnetic refrigeration materials working at temperatures near 120 K.

Magnetic phase transitions and magnetocaloric properties of (Gd12-xTbx)Co7 alloys

The structure and magnetocaloric properties of polycrystalline (Gd12-xTbx)Co7 (x=0, 4, and 8) alloys with Ho12Co7-type monoclinic structure have been investigated. A spin reorientation transition occurs at about 123 K for the alloy with x=0. The peak values of magnetic entropy change −ΔSM under a magnetic field change ΔH of 5 T is 8.8 J·kg−1·K−1 at 160.8 K (Tc), 8.2 J·kg−1·K−1 at 140.8 K (Tc), and 7.1 J·kg−1·K−1 at 118.9 K (Tc) for the alloys with x=0, 4 and 8, respectively. The refrigerant capacities reach 478, 327, and 160 J·kg−1 for x=0, 4, and 8, respectively. The relatively large magnetic entropy change and reversible magnetization behavior make these alloys a good choice for magnetic refrigeration applications in the temperature range of 118–160 K.

Elevating the temperature regime of the large magnetocaloric effect in a Ni–Mn–In alloy towards room temperature

We have prepared a Ni50(Mn,2%Cr)34In16 alloy by substituting Mn by Cr in a Ni50Mn34In16 alloy. A large isothermal magnetic entropy change is observed across the austenite–martensite phase transition in this new alloy for a moderate field change of 50 kOe. In comparison with the parent Ni50Mn34In16 alloy where the peak in isothermal entropy change amounts to nearly 19 J kg−1 K−1, in this Ni50(Mn,2%Cr)34In16 alloy the peak value of the isothermal entropy change is much larger, 24.4 J kg−1 K−1. Moreover, this large magnetocaloric effect in the Ni50(Mn,2%Cr)34In16 alloy occurs at ambient temperature near 294 K as compared with the temperature regime of the magnetocaloric effect being near 240 K in the parent Ni50Mn34In16 alloy. Thus the partial substitution of Mn by Cr in the Ni50Mn34In16 alloy is shown to be an effective method for enhancing the potential of the alloy system for near-room temperature applications.

The hydrogen absorption properties and magnetocaloric effect of La0.8Ce0.2(Fe1−xMnx)11.5Si1.5Hy

The effect of hydrogenating process on the homogeneity of hydrogen absorption in the La0.8Ce0.2(Fe1−xMnx)11.5Si1.5 compounds was investigated. It is attractive that the distribution of hydrogen atoms in the compounds becomes more uniform with increasing hydrogen pressure and annealing temperature. Homogeneous hydrides of La0.8Ce0.2(Fe0.985Mn0.015)11.5Si1.5 were obtained by annealing them at the temperature of 773 K and under the hydrogen atmosphere of 0.5 MPa. With changes of Mn content, the Curie temperatures (TC) of the hydrides of La0.8Ce0.2(Fe1−xMnx)11.5Si1.5 can be adjusted in the room temperature range from 279 to 312 K. Large magnetic entropy changes due to the itinerant-electron metamagnetic transition are obtained in the room temperature range for the hydrides of La0.8Ce0.2(Fe1−xMnx)11.5Si1.5.