Reversible Magnetocaloric Effect Research Articles

Large reversible magnetocaloric effects originating from ferromagnetic phase transition in Gd(Cu1−xNix)2 (x = 0.12, 0.15)

Here, the significant increase in MCE without any hysteresis loss was achieved through the substitution of nickel for a portion of the copper in GdCu2 compound. The values of maximum magnetic entropy changes (−ΔSMmax) and refrigeration capacity (RC) for Gd(Cu1-xNix)2 (x = 0.12, 0.15) compounds are 10.3 J/kg K, 455.3 J/kg, 9.3 J/kg K and 461.2 J/kg under varying magnetic fields from 0 to 5 T, respectively. The refrigeration capacity of Gd(Cu1−xNix)2 (x = 0.12, 0.15) is improved by an order of magnitude compared to the GdCu2 compound under varying magnetic fields from 0 to 5 T. While providing an ideal magnetocaloric refrigerated material for hydrogen liquefaction, our work also suggests a promising approach to the development of new magnetocaloric refrigerated materials.

Experimental study on coupled caloric effect driven by dual fields in metamagnetic alloy ErCo2

This study presents an experimental investigation of the coupled caloric effect driven by dual-fields in metamagnetic alloy ErCo2 with strong magneto-structural coupling. Magnetic measurements were conducted under different pressures, revealing that the application of hydrostatic pressure stabilizes a small volume of paramagnetism (PM) phase, resulting in a shift of the phase transition temperature towards the low-temperature region. This shift is opposite to the temperature associated with the magnetic field-driven phase transition. As pressure increases, the metamagnetic transition in ErCo2 is suppressed, and the hysteresis disappears. However, the produced cross-coupling caloric effect compensates the decrease in entropy change caused by the disappearance of the metamagnetic transition. As a result, a reversible giant magnetocaloric effect of 46.2 J/(kg·K) without hysteresis is achieved at a pressure of 0.910 GPa. Moreover, we propose that the temperature span of ErCo2 can be significantly widened by optimizing the thermodynamic pathway of the magnetic and pressure fields, overcoming the defect of a narrow temperature range.

Giant low-field magnetocaloric effect in unstable antiferromagnetic Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds

Magnetic refrigeration (MR) technology is regarded as an ideal solution for cryogenic applications, relying on magnetocaloric materials which provide necessary chilling effect. A series of polycrystalline Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds was synthesized, and their magnetic properties, magnetic phase transition together with magnetocaloric effect (MCE) were studied. The Tm1–xErxNi2Si2 (x = 0.2, 0.4) compounds display a field-induced metamagnetic transition from antiferromagnetic (AFM) to ferromagnetism (FM) in excess of 0.2 T, respectively. Meanwhile, the AFM ground state is unstable. Under the field change of 0–2 T, the values of maximal magnetic entropy change (−ΔSMmax) and refrigerant capacity (RC) for Tm0.8Er0.2Ni2Si2 compound are 17.9 J/(kg·K) and 83.5 J/kg, respectively. The large reversible MCE under low magnetic fields (≤2 T) indicates that Tm0.8Er0.2Ni2Si2 compound can serve as potential candidate materials for cryogenic magnetic refrigeration.

Enhanced magnetocaloric effect accompanying successive magnetic transitions in TbMn2Si2-xGex compounds

The lack of magnetic refrigeration (MR) materials with high magnetocaloric effect (MCE) and large relative cooling power (RCP) in the temperature range required for hydrogen liquefaction (20 K–77 K) is a bottleneck for practical applications of MR cooling systems. The present investigation of TbMn2Si2-xGex compounds (x = 0.1, 0.2) by variable temperature neutron and synchrotron X-ray diffraction, magnetization and heat capacity measurements, establish that substitution of Si with Ge in TbMn2Si2 leads to a significant enlargement of the unit cell and modification of the magnetic properties. Two consecutive ferromagnetic first-order transitions occur below 77 K with the third transition from paramagnetism to a collinear antiferromagnetic state being determined around 500 K. The resultant plateau-like MCE with large RCP below 77 K in these designed compounds offers scope for application for hydrogen liquefaction. Detailed neutron investigation confirm that four magnetic states exist within the temperature range 5 K to 500 K, with two successive first-order magnetic transitions below 77 K responsible for the large MCE. Our specific heat studies provide evidence of strong contributions from the nuclear specific heat and the corresponding nuclear specific heat coefficients of A = 430 ± 50 mJ mol−1 K and A = 418 ± 60 mJ mol−1 K have been determined for TbMn2Si2-xGex with x = 0.1 and x = 0.2, respectively. The overlapping entropy curves near these successive transitions lead to a plateau-like magnetothermal effect as well as a large reversible MCE for both samples (e.g. ΔSMmax = 14.0 J/kg K and ΔTmax = 7.6 K; RCP = 379 J/kg for TbMn2Si1.9Ge0.1 for an applied field of 5 T) indicating that the material can operate over a wide temperature range – particularly for hydrogen liquefaction.

Cryogenic magnetocaloric effect of the CaErAlO4 compound

The magnetism and magnetocaloric effect (MCE) of some rare-earth (RE)-based oxides have attracted special attention due to their interesting physical and chemical properties, such as easy fabrication and high chemical stability. In this paper, the CaErAlO4 polycrystal compound synthesized by the high-temperature solid-state method manifests the considerable second-order reversible MCE near the temperature of liquid helium. This compound crystallizes in the perovskite-like K2NiF4-type structure with the space group of I4/mmm. The negative paramagnetic Curie temperature suggests that antiferromagnetism is dominant in the material and the moderate magnetization is mainly contributed by the ferromagnetic interaction in the sample. The measured isothermal magnetic entropy changes (∆SM) at 3 K are 14.3 and 22.9 J/kg K under 0–20 and 0–50 kOe field changes, respectively. They are greater than those of most RE-based oxides. Our results indicate that the CaErAlO4 compound is a promising candidate for cryogenic magnetic refrigeration.

Rare‐Earth‐Free Mn30Fe20−xCuxAl50 Magnetocaloric Materials with Stable Cubic CsCl‐Type Structure for Room‐Temperature Refrigeration

AbstractMagnetic refrigeration technology based on the magnetocaloric effect (MCE) of magnetic substances has been considered a prominent, energy‐efficient, and environmentally benign cooling method. Exploring suitable magnetic substances is a prerequisite for practical applications. A family of rare‐earth‐free magnetocaloric materials called Mn30Fe20−xCuxAl50 alloys is identified room‐temperature refrigeration, which are derived from the well‐known MnAl‐based permanent magnets. As expected from experimental and theoretical investigations, all of the Mn30Fe20−xCuxAl50 alloys are crystallized in a stable cubic CsCl‐type crystal structure, revealing a single second‐order type magnetic phase transition (MPT) with tunable MPT temperature. They also exhibit a large reversible MCE and good magnetocaloric performances in a wide temperature range. Crucially, these Mn30Fe20−xCuxAl50 alloys represent a rare case of magnetic materials belonging to a large family that can be fabricated from low‐price, earth‐abundant, and non‐toxic elements. They could provide new choices for practical room‐temperature magnetic refrigeration applications.

Magnetism and cryogenic magnetocaloric effect of triangular-lattice LnOF (Ln = Gd, Dy, Ho, and Er) compounds

Frustrated lanthanide oxides with dense magnetic lattice and suppressed ordering temperature have potential applications in cryogenic magnetic refrigeration. Herein, the crystal structure, magnetic properties, magnetic phase transition (MPT) together with magnetocaloric effect (MCE) of LnOF (Ln = Gd, Dy, Ho, and Er) compounds were investigated. Crystallographic study shows that these compounds crystallize in the centrosymmetric space group Rm with an ideal triangular lattice. No long-range magnetic ordering is observed above 2 K for LnOF (Ln = Gd, Ho, and Er). However, DyOF compound undergoes an MPT from paramagnetic (PM) to antiferromagnetic (AFM) at the Néel temperature (TN ≈ 4 K). Considerable reversible MCE is observed in these triangular-lattice compounds. Under the magnetic field change (μ0ΔH) of 0–2 T, the maximum values of magnetic entropy change (–ΔSmax M) of them are 6.1, 9.4, 12.7, and 14.1 J/(kg·K), respectively. Interestingly, the value of ErOF with Ising-like spin is 2.3 times that of GdOF, which provides an approach for exploring magnetic refrigerants with excellent low-field cryogenic magnetocaloric effect.

Cyclic reversible martensitic transformation and magnetocaloric effect in a Ni51.0Mn20.8Ga22.4Cu5.8 alloy

Working materials exhibiting a large reversible magnetocaloric effect are necessary for improving the cooling efficiency of magnetic refrigeration. Herein, the cyclic reversibility of the martensitic transformation and magnetocaloric effect in a Ni51.0Mn20.8Ga22.4Cu5.8 alloy is investigated. The martensitic transformation exhibits small thermal and magnetic hystereses (∼6 K and ∼6.8 J/kg, respectively) and excellent reversibility upon 50 thermal and magnetic cycles owing to the good geometric compatibility of the martensite/austenite transferring interface. A reversible magnetic entropy change up to −21.7 J/kgK is achieved under 50 kOe after performing 50 magnetic cycles, indicating the excellent reversibility of the magnetocaloric effect in the alloy.

Large low-field reversible magnetocaloric effect in K3Gd(PO4)2 at sub-Kelvin temperature

We synthesized a potassium gadolinium phosphate K3Gd(PO4)2 with monoclinic structure (P21/m) by the high-temperature solid–state reaction method. Its lattice constants obtained by Rietveld refinements of XRD curve are a = 0.7411 nm, b = 0.5624 nm, and c = 0.9433 nm. Magnetic and magnetocaloric properties of K3Gd(PO4)2 were investigated in detail. The magnetic phase transition temperature of K3Gd(PO4)2 was determined by ultra-low temperature testing to be 0.58 K. K3Gd(PO4)2 exhibits large magnetic entropy changes (–ΔSM). The maximum –ΔSM are 20.2 and 29.4 J/(kg·K) in the magnetic field variation (ΔH) of 1 and 2 T, respectively, which are larger than that of the commercial Gd3Ga5O12 (GGG). The maximum adiabatic temperature change (ΔTad) reaches 5.91 K under a magnetic field change (ΔH) of 1 T. K3Gd(PO4)2 is a potential magnetic refrigeration material for obtaining sub-Kelvin temperatures.

Evidence of cluster glass phase, exchange bias, reversible magnetocaloric effect and study of electrical properties in Ni1−xCdxCr2O4 (x = 0–0.30) spinel

Evidence of cluster glass phase, exchange bias, reversible magnetocaloric effect and study of electrical properties in Ni1−xCdxCr2O4 (x = 0–0.30) spinel

Large reversible magnetocaloric effect across the first-order magneto-structural transition in (Mn0.45Fe0.55) (Ni0.6Co0.4) Si alloy

Magnetic materials with reversible magnetocaloric effect across their respective first-order magneto-structural transitions (MST) have vital significance for further advancement towards the ultimate goal of practical magnetic cooling applications. In this present study, the reversibility of the MST is investigated by analyzing the isofield curves under different minor and major thermal hysteresis loops and the isothermal curves under different magnetic field cycles. The reversibility of the magnetocaloric effect (MCE) depends upon the width of the nucleation energy barrier existing across the MST. Minor hysteresis loops are found to be minimizing the energy loss by preventing the nucleation of the martensite phase and can be easily returned to the austenite phase immediately while switching from cooling to heating. A large reversible isothermal magnetic entropy change ΔSM of −14.4 J kg−1 K−1 nearly at 322 K is observed for the (Mn0.45Fe0.55) (Ni0.6 Co0.4) Si alloy under a low magnetic field change of 3 T. The observed large reversible MCE, very low magnetic field-induced hysteresis loss, and large reversible RCeffe ∼ 155 J kg−1 will be beneficial for reducing the energy loss during several magnetic field cycles in practical cooling applications which makes this alloy promising for the development of efficient magnetic refrigerants.

Magnetic and Transport Anomalies and Large Magnetocaloric Effect in Cubic R4PtAl (R = Ho and Er)

We report the electronic properties of R4PtAl (R = Ho, and Er), which contains three sites for R, by the measurements of magnetization (ac and dc), heat-capacity, transport, and magnetoresistance (MR). Dc magnetization data reveal antiferromagnetic order below 19 K and 12 K in Ho and Er compounds, respectively. Additional features observed at lower temperatures (12 K for Ho4PtAl and 5 K for Er4PtAl) are akin to the cluster spin-glass phase. Resistivity data exhibit a weak minimum at a temperature marginally higher than their respective Néel temperature (TN), which is unusual for such rare-earths with well-localized 4f states. Isothermal magnetization and magnetoresistance data well below TN exhibit signatures of a subtle field-induced magnetic transition for a small magnetic field (<10 kOe). Notably, the isothermal entropy change at TN has the largest peak value within this rare-earth family; for a field change from zero to 50 kOe, the entropy change is ~14.5 J/kg K (Ho4PtAl) and ~21.5 J/kg K (Er4PtAl) suggesting a role of anisotropy of 4f orbital in determining this large value. The results provide some clues for the advancement of the field of magnetocaloric effect. The magnetocaloric property of Er4PtAl is nonhysteretic, meeting a challenge to find materials with reversible magnetocaloric effect.

Structural, magnetic and magnetocaloric properties of hexagonal MnCoGe-based thin films

The characteristic size of the magnetocaloric materials in magnetic refrigerators, thermomagnetic regenerators and energy harvesters is usually down to micrometer and nanometer length scales, which provides the largest possible contact surface area to the heat transfer liquid. Therefore, it is pivotal to investigate the structural, magnetic and magnetocaloric properties of magnetocaloric materials at micrometer and nanometer length scales. In the present study, we have successfully fabricated MnCoGe-based thin films using the pulsed laser deposition (PLD) technique. The as-deposited film shows a dense surface, homogeneous chemical distribution and a preferred orientation along the c-axis of the hexagonal Ni2In-type structure. In-situ temperature-dependent X-ray diffraction measurements on the as-deposited films reveal an irreversible structural degradation above 300 °C due to the considerable evaporation of the Mn atoms, which causes the formation of microscale pores in the films. The thermomagnetic behavior of the film annealed at 250 °C displays a reversible second-order ferromagnetic transition of the hexagonal phase at Curie temperature TC = 275 K, and a first-order hexagonal-orthorhombic structural transition below 200 K. The decoupling of the magnetic and structural transitions brings reversible magnetocaloric effect with the entropy change ΔS values of 2.5 J/(kgK) and the refrigeration capacity reaching 89 J/kg in Δμ0H = 5 T, which are comparable to other reported magnetocaloric thin films. Moreover, antiferromagnetic coupling in the low-temperature orthorhombic phase was observed, which has rarely been reported in the MnCoGe-based bulk alloys. The different magnetic ground states between the thin film and the bulk alloys may be originated from the strain effect imposed by the Al2O3 substrate. Consequently, this work not only provides insights into the structural, magnetic and magnetocaloric properties of the MnCoGe-based alloys at a nanometer length scale, but also offers a new idea for tailoring the multifunctional properties for this material family.

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.

Complete and reversible magnetostructural transition driven by low magnetic field in multiferroic NiCoMnIn alloys

Magnetic-field-induced first-order magnetostructural transition (MFI-FOMST) brings about an ample variety of intriguing magnetoresponsive effects including magnetocaloric effect, magnetoresistance and magnetostrain. Metamagnetic shape memory alloys (MSMAs) exhibit MFI-FOMST and thus giant magnetoresponsive effects, but the critical field for complete and reversible MFI-FOMST, (μ0∆H)min, is too high (usually >5 T), which has been a longstanding bottleneck for practical applications. Here, we successfully achieved complete and reversible MFI-FOMST under a low field of 1.5 T, which can be generated by permanent magnets, in a prototype MSMA. The significant reduction of (μ0∆H)min is realized by simultaneously enlarging the distance between Curie transition and magnetostructural transition and manipulating the geometric compatibility between the transforming phases. The low (μ0∆H)min provides a great opportunity for attaining low-field-induced large reversible magnetoresponsive effects. For instance, a large reversible magnetocaloric effect is achieved under 1.5 T. Our realization of low-field-induced complete and reversible first-order magnetostructural transition may push a significant step forward towards the practical use of MSMAs. This work is instructive for developing novel magnetic materials with low-field-actuated first-order phase transition for applications as magnetic actuators, magnetoresistors and solid-state refrigerants.

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.

Achievement of reversible table-like magnetocaloric effect in MnCo1-Gd Ge alloys around room temperature

• The table-like magnetocaloric effect in MnCo 1- x Gd x Ge alloys are achieved. • Two successive magnetic transitions appear in the MnCo 1- x Gd x Ge ( x = 0.04, 0.06). • The refrigerant capacity reach 282 J/kg in MnCo 0.94 Gd 0.06 Ge with Δ H = 50 kOe. • The relative cooling power reach 335 J/kg in MnCo 0.94 Gd 0.06 Ge with Δ H = 50 kOe. • The maximum temperature span are 128 K in MnCo 0.94 Gd 0.06 Ge with Δ H = 50 kOe. The structural, magnetic and magnetocaloric properties in the Gd doped MnCo 1- x Gd x Ge alloys were investigated. With the increase of Gd content, the coexistence of Ni 2 In-type hexagonal structure and TiNiSi-type orthorhombic structure appear from the pure Ni 2 In-type hexagonal structure of MnCoGe. All samples undergo the second-order magnetic transition (SOMT). MnCo 1- x Gd x Ge ( x = 0.04, 0.06) have two successive magnetic transitions and a large reversible table-like MCE has been achieved around room temperature (RT). Moreover, the relative cooling power ( RCP ) and effective refrigeration temperature span (δ T FWHM ) with the magnetic field change of 50 kOe reach 335 J/kg and 128 K, respectively.

Large reversible magnetocaloric effect and magnetoresistance by improving crystallographic compatibility condition in Ni(Co)-Mn-Ti all- d -metal Heusler alloys

Recently, all-$d$-metal Ni(Co)-Mn-Ti Heusler systems have become the research hotspot due to their magnetoresponsive properties associated with a tunable first-order magnetostructural transformation (MST) and excellent mechanical stability for potential applications. However, the presence of large thermal hysteresis acts as an obstacle to the cyclic operation of this novel material. In this present paper, we investigate a large reversible magnetocaloric effect (MCE) and magnetoresistance (MR) in ${\mathrm{Ni}}_{37\ensuremath{-}x}{\mathrm{Co}}_{13+x}{\mathrm{Mn}}_{34.5}{\mathrm{Ti}}_{15.5}$ all-$d$-metal Heusler alloys that undergo a first-order MST accompanied by a large magnetization change between ferromagnetic austenite and antiferromagnetic martensite phases. Tuning the small at.% of Co doping in ${\mathrm{Ni}}_{37\ensuremath{-}x}{\mathrm{Co}}_{13+x}{\mathrm{Mn}}_{34.5}{\mathrm{Ti}}_{15.5}$ systems, we achieved an optimum composition with $x$ = 1 where low thermal hysteresis of $\ensuremath{\sim}4.7$ K, a narrow transformation interval of $\ensuremath{\sim}11.2$ K, and improved sensitivity of transformation temperature $\ensuremath{\sim}2.8$ K/T is observed. In addition, the origin of small hysteresis is studied based on geometric compatibility between cubic austenite and monoclinic martensite phases, calculated from the powder x-ray diffraction data. These optimized parameters lead to a reversible magnetic field-induced inverse martensitic transition under the field cycling, yielding a large reversible magnetic entropy change ($\mathrm{\ensuremath{\Delta}}{\mathrm{S}}_{M}$) of $\ensuremath{\sim}17.78$ J ${\mathrm{kg}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at 277 K in a field change of 5 T. Moreover, a large reversible magnetoresistance (MR) of $\ensuremath{\sim}14%$ out of 32.6% is also obtained under 5-T magnetic field for $x$ = 1 sample in all-$d$-metal Heusler alloys. These reversible magnetoresponsive properties are comparable to other Ni-Mn-based Heusler alloys and have not been reported so far in the all-$d$-metal Heusler system. Therefore our present work demonstrates a pathway to design new cyclically stable multifunctional materials in all-$d$-metal Heusler systems for solid-state cooling devices and magnetic recording applications.

Large reversible cryogenic magnetocaloric effect in rare earth iron carbides of composition RE2FeC4 (RE=Ho, Er, and Tm)

At cryogenic temperatures, the investigations of magnetic phase transition and magnetocaloric effect in RE2FeC4 (RE = Ho, Er, and Tm) compounds were performed. Ho2FeC4 and Er2FeC4 compounds undergo two magnetic phase transitions with the temperature decreasing: from paramagnetic (PM) to ferromagnetic (FM) transition at their respective Curie temperature (TC) and from FM to antiferromagnetic (AFM) or ferrimagnetic (FIM) transition below 2 K. Tm2FeC4 compound exhibits only a second-order PM to FM phase transition at TC = 6 K. Large reversible MCE without hysteresis loss is observed in RE2FeC4 (RE = Ho, Er, and Tm) compounds. Particularly, the maximum value of magnetic entropy change (–ΔSM) is 21.62 J/(kg·K) under the magnetic field change (Δμ0H) of 0–5 T for Er2FeC4. The Er2FeC4 compound presenting excellent magnetocaloric performance makes it a competitive cryogenic magnetic refrigeration material.

Large reversible magnetocaloric effect in high-entropy MnFeCoNiGeSi system with low-hysteresis magnetostructural transformation

High-entropy alloys have attracted tremendous research interest in recent years because of their special functional properties. However, the investigations on the high-entropy alloys with thermal- and magnetic-field-induced magnetostructural transformation are still lacking. In this work, we provide a basic strategy to design a six-component MnFeCoNiGeSi high-entropy system, exhibiting low-hysteresis magnetostructural transformation between ferromagnetic orthorhombic and paramagnetic hexagonal phases. An increase in the configurational entropy is helpful to make the alloy crystallize in the single hexagonal structure, which can almost completely transform into the orthorhombic structure during cooling. The thermal hysteresis in our high-entropy alloy is as low as about 4.3 K. This advantage guarantees reversible magnetic-field-induced magnetostructural transformation and is accompanying a large magnetocaloric effect. A reversible entropy change of −13.67 J K−1 kg−1 is realized under a magnetic field variation of 0–5 T. The obtained room-temperature magnetocaloric performance is comparable to that of some rare-earth-based high-entropy alloys and conventional first-order magnetocaloric materials. Moreover, the geometric nonlinear theory of martensitic transformation is adopted to explain the origin of low hysteresis in our high-entropy alloys.