Magnetocaloric Effect Materials Research Articles

Exploring Magnetocaloric Materials for Sustainable Refrigeration near Hydrogen Gas Liquefaction Temperature

AbstractMagnetocaloric materials have the ability to undergo temperature changes when subjected to varying magnetic fields. These materials are of interest due to their potential for innovative cooling applications. This review article summarizes materials that exhibit magnetic ordering within the temperature range required for gas liquefaction and explores their potential applications through the magnetocaloric effect (MCE). The gas liquefaction temperature range is typically assumed to be 20–77 K, however, this study specifically summarizes materials that have a transition temperature near to the hydrogen liquefaction temperature (≈20K). This review article aims to showcase ongoing research on magnetic materials for hydrogen liquefaction. Driven by the depletion of natural resources and environmental concerns, the search for environmentally sustainable fuels has intensified, making hydrogen a promising alternative. However, the liquefaction of hydrogen is highly energy‐intensive. The investigation focuses on identifying and understanding these materials and assessing their suitability for environmentally friendly and sustainable cooling technologies. By harnessing the magnetocaloric effect, these materials exhibit temperature changes in response to an applied magnetic field, offering advantages over traditional cooling methods that are 20–50% more efficient. The review aims to furnish researchers with essential information that can help modify magnetocaloric effect (MCE) materials, enabling them to achieve the desired magnetic ordering temperature conducive to the liquefaction of hydrogen.

Design of Excellent Mechanical Performances and Magnetic Refrigeration via In Situ Forming Dual-Phase Alloys.

Magnetic refrigeration technology can achieve higher energy efficiency based on the magnetocaloric effect (MCE). However, the practical application of MCE materials is hindered by their poor mechanical properties, making them challenging to process into devices. Conventional strengthening strategies usually lead to a trade-off with refrigeration capacity reduction. Here, a novel design is presented to overcome this dilemma by forming dual-phase alloys through in situ precipitation of a tough magnetic refrigeration phase within an intermetallic compound with excellent MCE. In the alloy 87.5Gd-12.5Co, incorporating the interconnected tough phase Gd contributes to enhanced strength (≈505MPa) with good ductility (≈9.2%). The strengthening phase Gd simultaneously exhibits excellent MCE, enabling the alloy to achieve a peak refrigeration capacity of 720 J kg-1. Moreover, the alloy shows low thermal expansion induced by the synergistic effect of the two phases. It is beneficial for maintaining structural stability during heat exchange in magnetic refrigeration. The coupling interaction between the two magnetic phases can broaden the refrigeration temperature range and reduce hysteresis. This study guides the development of new high-performance materials with an excellent combination of mechanical and magnetic refrigeration properties as needed for gas liquefaction and refrigerators.

Analytical modeling of magnetocaloric effect in dense nanoparticle systems

AbstractDetermining the magnetocaloric effect (MCE) in dense nanoparticle systems (DNSs) poses a challenge due to the increased complexity of matter at the nanoscale. Given the interparticle magnetic interactions, diverse particle size and shape distributions, and the presence of inhomogeneous magnetic phases, selecting a suitable phenomenological model is essential to describe the temperature dependence of magnetic behavior in DNSs. Herein, we chose a cost‐effective Ni100‐xCrx DNS with adjustable magnetic transitions to showcase the resilience of the MCE across a broad temperature range (147–614 K). While the hyperbolic tangent model appears more fitting for materials with a single Curie temperature (TC), such as its parent bulk alloys, in the presence of a TC distribution a Gaussian distribution model proves to be better suited for DNSs. The latter model yields a magnetic entropy change, ΔSmax = 0.09–0.15 J kg‐K−1 in the DNS at a tiny field of 0.1T. The correlations between the broadening of the MCE peak and TC distribution are attributed to the particle size distribution and chemical inhomogeneity present in the DNS, paving the way for fine‐tuning MCE‐related properties such as the relative cooling power (13.17–33.45 J kg−1) and adiabatic temperature change (0.03–0.17 K). Our methodology not only enhances the potential for designing innovative MCE materials with broader operating ranges but also validates the universality of our phenomenological model for other families of nanocrystalline/nanogranular oxides/alloys thin films.

The magnetocaloric effect properties for potential applications of magnetic refrigerator technology: a review.

In the pursuit of a clean and environmentally friendly future, magnetic refrigerator technology based on the magnetocaloric effect has been proposed as a replacement for conventional refrigeration technologies characterized by inefficient energy use, greenhouse gas emissions, and ozone depletion. This paper presents an in-depth exploration of the current state of research on magnetocaloric effect (MCE) materials by, examining various types of MCE materials and their respective potentials. The focus is particularly directed towards perovskite manganite materials because of their numerous advantages over other materials. These advantages include a wide working temperature range, easily adjustable Curie temperature around room temperature, excellent chemical stability, cost-effective production processes, negligible magnetic and thermal hysteresis properties, as well as competitive values for -ΔSM and ΔTad compared to other materials. Additionally, crucial parameters defining the MCE properties of perovskite manganite materials are comprehensively discussed, both at a fundamental level and in detail.

Leveraging of both positive and negative magnetocaloric effects in ZnFe2O4 layers

The novel magnetocaloric thin film material with a tunable magnetic transition is the cornerstone of magnetic refrigeration, which plays a crucial role in cooling on-chip devices. Zn-ferrite (ZnFe2O4) occupies a significant place due to its interesting grain size-controlled magnetism. In this study, we investigate the magnetocaloric properties of Zn-ferrite layers consisting of a mixture of superparamagnetic (SPM), ferrimagnetic (FiM), and bulk-type antiferromagnetic (AFM) grains. Due to the co-existence of different magnetic grains, a crossover from the conventional magnetocaloric effect (MCE) to the inverse magnetocaloric effect (IMCE) is observed. The magnetic entropy change (-ΔSM) exhibits high-temperature positive values around the Curie temperature (TC) and low-temperature negative values around either the Néel temperature (TN) or blocking temperature (TB). The maximum value of -ΔSM (0.10 J/kg K) is almost double in AFM-dominant samples compared to SPM-dominant samples, while maintaining a relative cooling power (RCP) of 11.57–14.82 J/Kg under applied fields of 0 – 2T. FiM-dominant samples, with a wide working temperature window around room temperature, are suitable for large RCP applications. Thus, the discovery of new IMCE materials like single layers of Zn-ferrite is equally important in the search for suitable conventional MCE materials for magnetic refrigeration devices, which can exhibit multiple -ΔSM and RCP peaks in low and high temperatures.

Giant low-field reversible magnetocaloric effect at liquid helium temperature of niobium and iron co-substituted EuTiO3 compounds

Giant magnetocaloric effect (MCE) materials in the liquid helium temperature region have attracted a lot of attention in the field of low-temperature magnetic refrigeration (MR). In this study, a series of niobium (Nb) and iron (Fe) co-substituted EuTiO3 perovskites with cubic structure (space group pm3m) was successfully fabricated, and their magnetic properties as well as cryogenic magnetocaloric effects were investigated in detail. As expected, the introduction of Nb and Fe can significantly modulate the magnetic phase transition and magnetocaloric effect of the EuTiO3 compounds. With increasing Fe concentration, two local minima corresponding to the AFM-FM magnetic phase transition near 5.0 K and FM-PM transition near 10 K with no hysteresis in the thermomagnetic curves are observed, which is attributed to an enhancement of FM coupling. At the same time, the gradually widened –ΔSM–T curves and the two peaks with a broad shoulder lead to considerable refrigeration capacity (RC). With the field change of ΔH = 2 T, the calculated values of −ΔSMmax for the EuTi0.9375–xNb0.0625FexO3 (x = 0.075, 0.1, 0.125, 0.15) compounds are 24.2, 17.6, 14.5 and 14.0 J/(kg·K), respectively. The corresponding RC values were calculated to be 144.6, 138.3, 151.2 and 159 J/kg, respectively. Especially, the values of −ΔSMmax for EuTi0.8625Nb0.0625Fe0.075O3 are 8.6 and 15.1 J/(kg·K) under low field changes of 0.5 and 1 T, respectively. The giant low-field reversible magnetocaloric effect makes them attractive candidates for magnetic refrigeration in the liquid helium temperature region.

Er-Y-Cr-Si化合物在极低温区的巨低场磁热效应

Low-temperature and low-field magnetocaloric materials with high magnetocaloric effect (MCE) performance have important prospects in applications such as gas liquefaction. A series of polycrystalline Er1−xYxCr2Si2 (0 ≤ x ≤ 0.8) samples were successfully synthesized by arc melting, showing giant low-field MCE. For the sample with x = 0.1, the compound shows the best MCE performance, with the appropriate working temperature down to 2 K. Furthermore, the maximum value of magnetic entropy change ((−ΔSM)max) and adiabatic temperature change ((ΔTad)max) under the field change of 0–1 T are calculated to be 19.2 J kg−1 K−1 and 4.3 K correspondingly. The value of (−ΔSM)max is the largest ever reported for intermetallic MCE materials below 20 K. The characteristic of magnetic phase transition is verified to be of second order on basis of Arrott plots, mean field theory and rescaled universal −ΔSM curves. The physical mechanism indicates that the great enhancement of (−ΔSM)max as large as 15.9% due to 10% Y substitution originates from the larger saturation magnetic moments and the smaller saturated magnetic fields.

Magnetocaloric Effect in Lightly‐Doped Fe5Si3 Single Crystals

AbstractDevelopment of promising new materials for above room temperature magnetic cooling applications relies on careful balancing of structure and composition to maximize accessible metastable phases that can drive a strong magnetocaloric effect (MCE). However, the working temperatures of these materials may fall outside of desired application windows. In this work, it is shown that it is possible to control metastable phase stability temperatures of Fe5Si3 through selection of appropriate spin and charge doping. Here, the parent material's desired structure appears only within a narrow temperature range from 1098 to 1303 K. Doping with Mn and P is shown to allow stabilization of the parent's high temperature phase and resulting MCE to room temperature. The structural and magnetic properties, and the magnetocaloric effect of single crystal Fe4.83Mn0.16Si2.91P0.09 (FMSP) are investigated experimentally and theoretically. A first‐order magneto‐elastic transition is observed at 348 K, where magnetic onset is accompanied by a change in lattice volume without an apparent change in crystal symmetry. Although the trace Mn and P doping are found to decrease the TC, the maximum magnetic entropy change ΔSMax(T) and the relative cooling power (RCP) of FMSP are enhanced compared to polycrystalline Fe5Si3. As a result, an intrinsically broader entropy change over a larger temperature span is generated in the lightly doped single crystal of Fe5Si3. The magnetic moment of the system is also enhanced. Density functional theory (DFT) calculations are performed to gain microscopic insights into the experimental findings. The results suggest that the hexagonal Fe5Si3 is a new giant room temperature MCE material that is on par with La–Fe–Si and Fe‐Mn‐P‐Si systems.

A new method to enhance the magnetocaloric effect in (Sc,Ti)Fe2 via magnetic phase separation

Magnetic refrigeration based on the magnetocaloric effect (MCE) is a novel refrigeration technology that will replace traditional vapor-compression refrigeration in the future. Improvement in the performance of MCE materials is crucial for the development of magnetic refrigeration technology. This study presents a new method that enhances the MCE performance of (Sc,Ti)Fe2 via magnetic phase separation. The maximum magnetic entropy change induced by the coexistence of an in-plane ferromagnetic phase (FMab) and a canting antiferromagnetic phase (CAFM) in Sc0.3Ti0.7Fe2 is twice that found in other (Sc,Ti)Fe2 compounds. Variable-temperature neutron diffraction experiments directly reveal that the large magnetic entropy change in Sc0.3Ti0.7Fe2 is dominated by the transformation from a highly ordered FMab state to a CAFM state with a lower magnetic order. The magnetic phase separation is a direct transition from a higher-ordered state with a larger lattice to a lower-ordered state with a smaller lattice that induces a large magnetic order change and lattice contraction. The combination of the metamagnetic transition and negative thermal expansion leads to enhanced MCE. This study suggests the possibility that magnetic phase separation can be an effective approach to achieving and controlling a large MCE in magnetic materials.

Magnetic properties and universal behaviour of magnetocaloric effect for polycrystalline [formula omitted] compound

In the present study, we have systematically investigated the magnetic and magnetocaloric properties as well as the universal behaviour of magnetocaloric effect (MCE) for polycrystalline (Nd0.5Sm0.5)0.5Sr0.5MnO3 compound. The universal behaviour of magnetic entropy change is proposed here for conventional magnetocaloric effect (CMCE) materials with second order phase transition. Thus, the construction of a universal master curve for MCE is possible in our system by rescaling the temperature axis. For such CMCE compounds, ΔS follows the power law dependence of H: ΔS ∝ Hn where ‘n’ is dependent on both H and T. In this paper, we have studied the universal behaviour of MCE at different conditions of initial and final field values. The result suggests that the universality behaviour of MCE is satisfied if and only if the initial base field remains zero or at a constant value.

Structural and cryogenic magnetic properties of the RE2MoO6 (RE = Er and Ho) compounds

The rare earth (RE) based magnetic materials with large low temperature magnetocaloric effect (MCE) have attracted much research interest due to their potential application for the environment-friendly magnetic refrigeration (MR) technology. Herein, a systematic investigation on the crystal structure, micro morphology together with the low temperature magnetic properties and MCE performances have been conducted on the RE2MoO6 (RE = Er and Ho) compounds. Both compounds crystallize in monoclinic structure and exhibit large reversible low temperature MCE. The maximum magnetic entropy changes (−ΔSMmax) at magnetic field change (ΔH) of 0–5 T reach 15.3 and 15.8 J kg−1 K−1 for Er2MoO6 and Ho2MoO6, respectively. The corresponding relative cooling power/refrigeration capacity (RCP/RC) values are 197.4/149.7 and 286.0/222.3 J/kg. These obtained MCE parameters for present RE2MoO6 compounds are close to those of reported RE based MCE materials, which make them of potential for low temperature MR application.

The effects of Tb doping on the negative and positive magnetocaloric effects of Mn3Ga1−xTbxC (0.02 ≤ x ≤ 0.05)

Generally, researchers focus on the great negative magnetocaloric effect (NMCE) rather than the positive magnetocaloric effect (PMCE) in Mn3GaC. Here, we prepared Mn3Ga1−xTbxC composites with a partial substitution of Ga by Tb. Tb doping expands the canted-ferromagnetic phase (CFM) between the anti-ferromagnetic and ferromagnetic phase in Mn3Ga0.97Tb0.03C. The CFM phase can be as a boundary to separate the NMCE from PMCE. It is possible to combine the NMCE and PMCE for refrigeration. Compared with NMCE in Mn3GaC, NMCE–PMCE combination in Mn3Ga0.97Tb0.03C displays a much larger operating temperature range without loss of magnetic entropy changes. Therefore, the NMCE–PMCE combination is valuable for improving the operating temperature range of magnetocaloric effect materials. It also provides a new idea for refrigeration applications.

A REVIEW OF MECHANOCALORIC REFRIGERATION DEVICES FROM 2012 TO 2020

Solid-State room temperature refrigeration devices have been reported extensively in the last decades with a focus on magnetocaloric effect materials, a thermal response to an applied magnetic field in a solid refrigerant. Currently, the limitations to generate large magnetic fields needed for better efficiencies have posed a challenge to rival current standard vapor compression cycles. Conventional refrigerants in standard vapor cycles are expected to contribute to global warming close to 25000 kgCO2,eq over the next 100 years. The need to overcome such challenges has driven a search for alternative i-caloric effects such as electrocaloric which is the thermal response of the material to the application of an electric field and mechanocaloric, a thermal response to the application of a stress field. Recently, the latter effect is being reported and categorized by the type of stress field applied. They are named elastocaloric for uniaxial stress, barocaloric for isostatic stress, and torsiocaloric for pure shear. Due to its simple stress, elastocaloric regenerators with shape memory alloys (SMA) were reported first. With a design similar to shell-tube heat exchanger with SMA being the shell and tubes while the heat transfer fluids (HTF) flows within the tubes. Promising thermodynamic cycle parameters such as coefficient of performance COP 11.0 with a temperature span of 24.6 K subject to a strain of 4.5% have been achieved with this design. Another device was reported working in a continuous non-regenerative manner with steady state being reached within seconds presented COP of 9.5 and a heat load of 250 W for a temperature span of 10K. As for barocaloric materials some researchers announced that are currently developing devices with these phenomena. Its main challenge is to elaborate a design that allows cyclic isostatic stress application, usually achieved by encapsulating the barocaloric material. One research group presented a study on a simulated active barocaloric regenerator on metal alloys and Acetoxy Silicone Rubber (ASR). The most recent mechanocaloric effect is the torsiocaloric. Two devices for measuring the torsiocaloric effect where presented, one in a batch form and another setup similar to a heat exchanger shell-tube where the tube is the solid-state refrigerant that can be twisted while in direct contact with the HTF flowing on the shell side. Thus, we aim to provide an in-depth analysis of recent studies of mechanocaloric devices describing their working cycles, thermodynamic parameters, HTF circuits and comparing their design choices, and forecast the design of near future mechanocaloric solid-state devices.

The nature of the metamagnetic transition in Heusler alloy Ni44.9Mn43In12.1 studied for magnetic refrigeration application

The nature of the phases, phase transitions, and their magnetic characteristics all play an essential role in the performance of Ni-Mn-In Heusler alloys, both as magnetic shape memory and giant magnetocaloric effect (MCE) materials. The details of the structural and magnetic transformations in Ni 44.9 Mn 43 In 12.1 Heusler alloy are reported in this work, using synchrotron and neutron diffraction and AC-SQUID susceptibility results. Of special interest is the affirmation of an antiferromagnetic (AFM) phase and the exclusion of a spin-glass state as the cause of the observed drop in magnetization upon cooling. This is of critical importance for magnetocaloric applications because of the dominant contribution to MCE of the magnetic entropy change upon phase transformation. • The magnetic and crystallographic nature of Ni 44.9 Mn 43 In 12.1 , were studied using synchrotron and neutron diffraction and AC-SQUID. • Cooling below 304 K results in ferromagnetic to antiferromagnetic transition; critically important for the magnetocaloric effect. • The crystallographic and magnetic transformations from austenite to martensite and from ferromagnetic to antiferromagnetic, coincide. • The hysteresis of the crystallographic transition is narrow, an advantage for MCE and other applications.

Magnetic and anisotropic magnetocaloric effects of HoCoSi fast quenching ribbons

The performance of magnetocaloric effect materials is one of the key factors restricting the development of magnetic refrigeration technology. Materials with anisotropic magnetocaloric effect can be used in the rotary magnetic refrigeration technology, which is beneficial to the simplification of refrigeration devices. In this work, the magnetic properties, magnetocaloric effects, and magnetic anisotropies of rapidly quenched HoCoSi compounds are investigated. At low temperatures below <i>T</i><sub>t</sub> = 5.7 K, the HoCoSi ferromagnetism and helical magnetism coexist. With the increase of temperature, the HoCoSi undergoes a second-order phase transition from ferromagnetic (FM) to paramagnetic (PM) phase at <i>T</i><sub>C</sub> = 13.7 K. Both XRD and SEM show that the HoCoSi has a preferred orientation. In order to obtain a large magnetocaloric effect and to determine the effect of preferred orientation on magnetism and magnetocaloric effect, the isothermal magnetization curves of the 10 m/s–HoCoSi fast quenched belt in the directions of <i>H</i> parallel and perpendicular to texture around the Curie temperature are analyzed. The corresponding magnetic entropy change (–Δ<i>S</i><sub>M</sub>) and magnetic refrigeration capacity (RC) are calculated. Under the magnetic field changing from 0 to 5 T, the value of –Δ<i>S</i><sub>M</sub> is 22 J/(kg·K) in the direction of <i>H</i> parallel to the texture and 12 J/(kg·K) in the direction of <i>H</i> perpendicular to texture , and their corresponding values of RC(RCP)are 360 (393.8) J·kg<sup>–1</sup> and 160 (254.4) J/kg. The value of –Δ<i>S</i><sub>M</sub> reaches 12.5 J/(kg·K)even at <i>μ</i><sub>0</sub><i>H</i> = 0–2 T in the direction of H parallel to the texture. It is obvious that the 10-m/s-HoCoSi fast quenching belt shows a large low-field magnetocaloric effect and obvious magnetic anisotropy, which is expected to be used to realize the magnetic refrigeration technology of rotating samples.

Excellent cryogenic magnetocaloric performances in ferromagnetic Sr2GdNbO6 double perovskite compound

The solid state magnetic cooling (MC) method by utilizing the magnetocaloric effect (MCE) has been recognized as an environmentally friendly and energy efficiency technology. A huge gap between the developing of MCE materials and the practical MC applications still exists at present. In this work, a combination theoretical and experimental investigation of the Sr2GdNbO6 compound with a typical orthorhombic double perovskite (DP) type structure in terms of structural, magnetic and MCE properties have been reported. Ferromagnetic (FM) interaction with large magnetic moment at ground state has been confirmed in Sr2GdNbO6 DP compound. Excellent MCE performances at cryogenic have been realized in Sr2GdNbO6 DP compound which is accompanied by a second-ordered type magnetic transition from paramagnetic to FM state. The observed large MCE parameters make the Sr2GdNbO6 DP compound attractive for practical cryogenic MC applications.

Large reversible magnetic entropy change of R3Ni6Al2 (R = Dy, Ho and Er) compounds

Large magnetocaloric effect (MCE) and magnetic properties in R3Ni6Al2 (R = Dy, Ho and Er) compounds were systematically investigated. Large magnetic moment and low magnetic transition temperature play a decisive role in the magnetocaloric performance for R3Ni6Al2 (R = Dy, Ho and Er) compounds. Ho3Ni6Al2 compound shows the largest magnetic entropy change with the value of 19.7 J/kg K at ~20 K under field change of 0–5 T because of the large magnetic moment and moderate transition temperature. For Dy3Ni6Al2 compound, it exhibits the largest refrigeration capacity with the value of 394.5 J/kg due to the successive magnetic transitions. The Er3Ni6Al2 compound has a large MCE at ultra-low temperatures around 4 K. Furthermore, the second-order phase transition in R3Ni6Al2 (R = Dy, Ho, Er) compounds were confirmed according to Arrott plots, rescaled universal magnetic entropy change curves and mean field theory with negligible thermal and magnetic hysteresis. The large reversible MCE with low working temperatures indicates that R3Ni6Al2 compounds are potential excellent MCE materials for low-temperature magnetic refrigeration.

Sign of lattice and spin entropy change during phase transition in giant magnetocaloric materials

<p indent=0mm>Solid-state refrigeration based on the magnetocaloric effect (MCE) has garnered worldwide attention because of its superior energy conservation and environment friendliness. A common feature of giant magnetocaloric materials is the simultaneous magnetic and lattice transitions, while some of them undergo negative expansion, i.e., lattice contraction, during the transition from the ferromagnetic (FM) to the paramagnetic (PM) phase. Generally, a larger lattice volume indicates softer phonons and therefore a larger phonon entropy. However, experimental and theoretical studies have shown that there are great differences in the mechanism of phonon modes for different materials. In particular, the strengthening or softening of the phonon vibration mode during magnetic phase transition determines the magnitude and sign of lattice entropy change. Therefore, for the giant MCE materials with negative thermal expansion, whether the sign of lattice and spin entropy change is the same or the opposite has always been controversial. Combined with previous studies of nuclear resonance inelastic X-ray scattering (NRIXS), and by means of heat flow measurements and Debye theory calculations, we have clarified the sign of lattice and spin entropy change of giant magnetocaloric La(Fe, Si)₁₃-based compounds and MM<italic></italic>X alloys with negative thermal expansion. Results show that the lattice and spin entropy changes retain the same sign for La(Fe, Si)₁₃-based compounds and MM′X (M, M′ = transition element, X = main element) alloys, which conforms to the principle of entropy increase. This work is helpful in fully understanding the intrinsic mechanism of giant magnetocaloric effect and its multi-field regulation for magnetostructural/magnetoelastic materials with negative thermal expansion during phase transition.

Significant reduction of phase-transition hysteresis for magnetocaloric (La1-xCex)2Fe11Si2Hy alloys by microstructural manipulation

First-order magnetostructural phase transitions are inevitably accompanied by large hysteresis, which evokes non-ignorable energy losses a main challenge for the utilization of giant magnetocaloric effect (MCE) materials in the emerging magnetic cooling technology. In this work, we present a novel approach to reduce the hysteresis and simultaneously to remain the giant entropy change in La-Fe-Si-based MCE alloys by microstructural manipulation. The microstructure evolution is comprehensively studied by high angle annular dark field-scanning transmission electron microscope, three-dimensional atom probe and geometric phase analysis. For the LaFe13-xSix system via co-doping of Ce and H atoms, we have observed the appearance of nanograins in size range of 5 – 50 nm that is totally different from the widely reported compositions. Such refinement can be ascribed to the release of internal stress caused by the inhomogeneous distribution of hydrogen atoms. With the formation of the nanocrystals in (La1-xCex)2Fe11Si2Hy alloys, the value of hysteresis loss can be monotonously reduced from 48.3 to 0.6 J kg−1. More importantly, the magnetostructural transition keeps an obvious first-order type, which leads to a large adiabatic temperature change of 2.03 K in 1.3 T upon 105 magnetic cycles, as well as a high reversible refrigeration capacity of 89.4 J kg−1 for (La0.6Ce0.4)2Fe11Si2Hy.

Manufacture and characterization of HoErCo medium-entropy alloy microwires with excellent magnetic entropy change

A melt-extracted HoErCo medium-entropy alloy (MEA) with large magnetic entropy change and excellent magnetic refrigerant capacity is successfully designed in this study. The microstructure evolution of these microwires near room temperature is studied by an in-situ high energy synchrotron X-ray diffraction (HEXRD). The wires show typical amorphous characteristics during room temperature to 250 K. For a field change of 5 T, the maximum magnetic entropy change (-ΔSMmax) of the microwires reaches a maximum value of 15.0 J•kg−1 K−1. Magnetization measurements revealed a paramagnetic to ferromagnetic phase transition at TC~16 K. The refrigerant capacity (RC) and relative cooling power (RCP) are 527 J•kg−1 and 600 J•kg−1, respectively. This investigation highlights the potential of HoErCo MEA microwires as promising magnetocaloric effect materials for cryogenic applications of magnetic cooling.