Maximum Magnetic Entropy Change Research Articles

Fine tuning of Mn/Co vacancies for optimized magnetocaloric performance in MnCoGe alloys

As a family of rare-earth-free magnetocaloric materials, MnCoGe-based alloys have attracted intensive attention in the past few years. In this study, we reveal that the deficiency of either Mn or Co reduces the valence electron concentration of MnCoGe system, thereby lowering its structural transition temperature (Ttr) by pushing the Fermi level away from the Mn-Mn antibonding electronic states. Moreover, Ttr is found to be more sensitive to Co content. By systematically analyzing the temperature dependent magnetization plots and Arrott curves, it is proven that the magnetic and structural degrees of freedom are coupled in the Mn0.97CoGe alloy, resulting in a first-order magnetic phase transition. On the contrary, MnCo0.98Ge undergoes a second-order transition. As a consequence, the Mn0.97CoGe alloy exhibits a maximum magnetic entropy change of 27.6 J kg−1K−1 under a magnetic field of 5 T near the Curie temperature of 265 K, corresponding to a refrigeration capacity of 212.1 J kg−1. Our work demonstrates Mn/Co vacant MnCoGe alloy as a robust candidate of magnetic substance for room temperature magnetocaloric refrigeration.

STRUCTURAL, MAGNETIC AND MAGNETOCALORIC PROPERTIES OF La0.7Sr0.2Ba0.1MnO3 MANGANITE

In this present work, the structural, magnetocaloric and magnetic properties of La0.7Sr0.2Ba0.1MnO3 (LSBM) manganite were investigated. The material was synthesized using the sol-gel method and X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) devices were used to analyze structural properties such as crystal structure and surface morphology. XRD measurement revealed that the crystal structure of LSBM manganite is hexagonal. Based on the magnetic measurements, the TC value of La0.7Sr0.2Ba0.1MnO3 manganite compounds was calculated as 362 K. The ∆SM value of sample is established as 2.79 Jkg-1K-1 in an applied magnetic field of 5T. Arrott curves revealed that the phase transition was second order.

Implementation of Backpropagation Neural Network for Prediction Magnetocaloric Effect of Manganite

In the field of magnetic cooling technology, there is still much to learn about the magnetocaloric properties of magnetic cooling materials. Research into magnetocaloric manganites exhibiting a significant maximum magnetic entropy change in the vicinity of ambient temperature yields encouraging outcomes for the advancement of magnetic refrigeration apparatus. Through a combination of chemical substitutions, changes in the amount of oxygen present, and different synthesis techniques, these manganites undergo lattice distortions that result in pseudocubic, orthorhombic, and rhombohedral structures instead of perovskite cubic structures. The present investigation used backpropagation neural networks (BPNNs) to investigate the correlations among maximum magnetic entropy change (MMEC), Curie temperature (Tc), lanthanum manganite compositions, lattice properties, and dopant ionic radii. Simbrain 3.07 was used to execute the BPNN model, and the suggested model accuracy was examined using coefficient determination. As a result, the model's predicted values for the mean absolute error, root mean square, and coefficient correlation for MMEC are 0.012, 0.022, and 0.9861, respectively. The model predicts that the Curie temperature mean absolute error, root mean square, and coefficient correlation will be 0.015, 0.021, and 0.9947, respectively. Based on these results, BPNN has the potential to be applied in predicting the MMEC and Tc of manganite as preliminary decision during experiments.

Elastic, electronic, magnetic and magnetocaloric properties of janus MnXO (X=S, Se and Te) monolayers: First-principles and Monte Carlo investigations

In this work, we present the first theoretical analysis of the elastic, electronic, magnetic and magnetocaloric properties of 1T-phase Janus MnXO (X = S, Se and Te) monolayers using first-principle calculations based on density functional theory combined with Monte Carlo simulation. The stability of the studied monolayers has been analyzed by using the elastic constants Cij and formation energy, which indicate that all monolayers are stable. Moreover, the electronic properties reveal the metal characteristics of all monolayers, with a total magnetic moment of 3.25 μB, 3.81 μB and 4.09 μB for MnSO, MnSeO, and MnTeO, respectively. Further, the extracted critical temperature values (Tc) from Monte Carlo simulation are Tc = 115 K, Tc = 130 K and Tc = 82 K, for MnSO, MnSeO and MnTeO, respectively. Interestingly, the predicted maximum magnetic entropy change −ΔSmax and maximum relative cooling power RCP (and adiabatic temperature change) are 10,38 J/kg.K and 763,43 J/kg (7,11 K) for MnSO, 6,79 J/kg.K and 515,57 J/kg (3,25K) for MnSeO, and 6,39 J/kg.K and 407,16 J/kg (3,46 K) for MnTeO at a magnetic field of 5T. These results suggest that the Janus MnXO (X = S, Se and Te) monolayers are a potential materials for use in magnetic nanodevices and low-dimensional magnetic refrigeration.

Cryogenic magnetocaloric effects of NaLnF4 (Ln = Gd, Tb, Dy, Ho, Er, Tm, and Yb)

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

Geometrically frustrated Gd2Ti2O7 oxide: A comprehensive exploration of structural, magnetic, and magnetocaloric properties for cryogenic magnetic cooling applications

The magnetocaloric effect (MCE) has been extensively studied in various magnetic solids, aiming to both facilitate practical applications in magnetic cooling and deepen our understanding these materials’ intrinsic properties. This study presents a systematic investigation of Gd2Ti2O7 oxide, characterized by a geometrically frustrated magnetic structure, focusing on its structural and magnetic characteristics through experimental analysis and theoretical calculations. Emphasis is placed on its magnetic phase transition (MPT) and magnetocaloric properties, scrutinizing temperatures as low as 0.4 K and magnetic fields up to 16 T. The results reveal that Gd2Ti2O7 oxide possesses a crystalline cubic pyrochlore-type structure with an antiferromagnetic (AFM) semiconductor ground state. The material undergoes a first-order MPT in low field and low-temperature regimes, transitioning to a second-order MPT above 2 K up to 16 T. Evaluation of magnetocaloric parameters, including maximum magnetic entropy change, temperature-averaged entropy change, relative cooling power, and refrigerant capacity, indicates moderate values under low magnetic field changes, while significantly large values are achievable under high magnetic field changes. This finding suggests that potential cryogenic magnetocaloric materials (MCMs) with optimal performance should exhibit low MPT temperatures induced by magnetic frustration and possess a ground state with a sufficiently large magnetic moment induced by low magnetic fields, thus avoiding excessively strong AFM coupling. This study lays the groundwork for future cryogenic MCM design and provides valuable insights into the intrinsic properties of geometrically frustrated magnetic materials.

Magnetocaloric effect and applied refrigeration performance of La(Fe,Si)13-based compounds

As a solid-state refrigeration technology, room-temperature magnetic refrigeration has several significant advantages comparing with conventional gas compression refrigeration, such as environmental friendliness, high energy efficiency and dependable operation. In the present study, the magnetocaloric effect and applied refrigeration performance of La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds were studied systematically. All alloys crystallize mainly in NaZn13-type phase with trace α-Fe phase between 1.36 and 1.80 wt%. The necessary heat treatment improves the formation of main phase. As x increases, the Curie temperature (Tc) decreases gradually from 295.3 K to 273.0 K. All alloys undergo strong field-induced first-order itinerant-electron metamagnetic transition. Under 0–1.5 T, the maximum magnetic entropy changes (-ΔSM)max for La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds vary from 10.9 J/(kg K) to 13.5 J/(kg K). And the maximum adiabatic temperature changes (ΔTad)max vary from 2.7 K to 3.9 K. To study the applied refrigeration performance, a rotary magnetic refrigerator is designed successfully, whose refrigeration temperature and cooling power meet the requirement of cold storage. Successful large-quantity preparation, giant magnetocaloric effect and excellent refrigeration performance suggest that, La0.8Ce0.2Fe11.6-xMn0.15+xSi1.25Al0.1H1.8 (x = 0, 0.03, 0.06, 0.09, 0.12) compounds can be used as the promising candidates for magnetic refrigerants.

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.

The magnetic and electronic properties of Ho6Fe23−xCox (x = 0, 1, 2, 3)

Magnetic and electronic properties of Ho6Fe23−xCox (x = 0, 1, 2, 3) compounds were investigated for the first time by experimental measurements on their polycrystalline samples combining with first-principles calculation. The samples of Ho6Fe23−xCox were successful prepared by a vacuum arc furnace. The XRD analysis and Rietveld refinement results show that Ho6Fe23−xCox crystallize in a face-centered cubic Th6Mn23-type structure with space group Fm3¯m (No.225), and their lattice parameters decrease with the increasing Co content. The M−T curves indicates that AFM-FM transition occurred at Neél temperature TN, the FM-PM transition occurred at Currie temperature TC for Ho6Fe23−xCox and the FM-PM transition belongs to a second-order transition. The Currie temperature and magnetic compensation temperature for all the samples increases with the increase of the content of Co. The maximum magnetic entropy change (-ΔSM) for the Ho6Fe23−xCox compounds under an applied magnetic field of 15 k Oe are 0.594, 1.023, 0.726 and 0.48 J kg−1 K−1 around their Currie temperature (TC = 542, 580, 622 and 654 K), respectively. This relatively large -ΔSM of Ho6Fe23−xCox occurred in a relatively high temperature region and under low applied magnetic field, pointing to the potential application as magnetic refrigeration materials using at higher temperature. The experimental results show that Co doping can regulate the magneto-thermal properties of the materials, so as to improve the magnetic entropy change of the existing magnetic refrigeration materials. The electronic properties of Ho6Fe23−xCox was studied by using the first-principle calculation. The band structures and density of states indicate that Ho6Fe23−xCox are good conductor.

Magnetoelastic Coupling Evidence by Anisotropic Crossed Thermal Expansion in Magnetocaloric RSrCoFeO6 (R = Sm, Eu) Double Perovskites.

Double perovskite oxides, characterized by their tunable magnetic properties and robust interconnection between the lattice and magnetic degrees of freedom, present an enticing foundation for advanced magnetic refrigeration materials. Herein, we delve into the influence of rare-earth elements on RSrCoFeO6 (R = Sm, Eu) disordered double perovskites by examining their structural, electronic, magnetic, and magnetocaloric properties. Temperature-dependent synchrotron X-ray diffraction analysis confirmed the stability of the orthorhombic phase (Pnma) across a wide temperature range. X-ray photoemission spectroscopy revealed that both Sm and Eu are in the 3+ state, whereas multiple states for Co2+/3+ and Fe3+/4+ are identified. The magnetic investigation and magnetocaloric effect (MCE) analysis brought to light the presence of a long-range antiferromagnetic (AFM) order with a second-order phase transition (SOPT) in both samples. The maximum magnetic entropy change ΔSMmax was approximately 0.9 J/kg K for both samples at applied field 0-7 T, manifesting prominently above Neel temperatures TN ≈ 93 K (Sm) and 84 K (Eu). Nevertheless, different relative cooling powers (RCP) of 112.6 J/kg (Sm) and 95.5 J/kg (Eu) were observed. A detailed analysis of the temperature-dependent lattice parameters shed light on a distinct magnetocaloric effect across the magnetic transition temperature, unveiling an anisotropic thermal expansion [αV = 1.41 × 10-5 K-1 (Sm) and αV = 1.54 × 10-5 K-1 (Eu)] wherein the thermal expansion axial ratio αbSm/αbEu = 0.61 became lower with increasing temperature, which suggests that the Eu sample experiences a greater thermal expansion in the b-axis direction. At the atomic bonding level, the evidence for magnetoelastic coupling around the magnetic transition temperatures TN was found through the anomalies along the average Co/Fe-O bond distance, formal valence, octahedral distortion, as well as an anisotropic lattice expansion.

Melting of the charge-ordered state in Y0.5Ca0.5MnO3 through Ru-substitution and consequent development of ferromagnetic and magnetocaloric behavior

The effect of Ru-substitution (5–15 %) on the charge ordering of Y0.5Ca0.5MnO3 has been investigated in this paper. Ru, existing in different oxidation states such as Ru4+ and Ru5+, plays an immense role in causing ferromagnetic (FM) superexchange interactions with Mn3+ ions. This, combined with the FM double-exchange interactions between Mn3+ and Mn4+ ions, destroys charge ordering. The development of ferromagnetism in Ru-substituted compounds is understood experimentally through the remarkable enhancement of dc magnetization with a simultaneous shift of TC from 57 K to 95 K with increasing Ru content from x = 0.05 to x = 0.15. The appearance of hysteresis for higher doping concentrations further confirms the FM nature. Concomitant with the favorable impact on the magnetic nature, there is also a development of magnetocaloric properties upon Ru-substitution. The maximum magnetic entropy change for x = 0.05 to 0.15 that was found to peak at TC ranges from 1.08 J/kg/K to 2.8 J/kg/K respectively for a field change of 9 T. The corresponding relative cooling power (RCP) increases from 76 J/kg to 324 J/kg indicating a significant growth of RCP with Ru substitution. These salient features of Ru-doped Y0.5Ca0.5MnO3 would make it a suitable candidate for magnetic refrigeration.

Room-temperature magnetocaloric properties of yLa0.67Ca0.27Sr0.06MnO3/1−yLa0.7Sr0.3Mn0.95Cu0.05O3 composites

In this study, we have characterized the magnetic and magnetocaloric (MC) properties of composites formed by two manganites with appropriate Curie temperatures (TC) and acceptable maximum magnetic entropy change (-ΔSMmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{{\ ext{M}}}^{{\ ext{max}}}$$\\end{document}) values. The composites have similar diffraction patterns obtained for the main phases La0.67Ca0.27Sr0.06MnO3 (LCSM) and La0.7Sr0.3Mn0.95Cu0.05O3 (LSMC) overlapping the diffraction peaks of the perovskite structure. The absence of any diffraction peaks distinct from the main phases in the XRD patterns of the composites indicates that there is no third phase besides the main ones. It is understood from the SEM images that the composites are composed of particles of different shapes and that the interparticle spacing decreases and the grain boundaries become clear, indicating that the interaction between particles becomes stronger with the increase of the y ratio. A gradual transition is seen from the M(T) curves, which specify that the composites consist of phases with discrete transition temperatures. The magnetic phase transition of the samples is second order. The -ΔSMmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{{\ ext{M}}}^{{\ ext{max}}}$$\\end{document} value has been calculated as 3.18, 3.24, and 4.05 J kg−1 K−1 at 5 T magnetic field for the composites 0.25LCSM/0.75LSMC, 0.50LCSM/0.50LSMC, and 0.75LCSM/0.25LSMC, respectively. Since the RCP value of 0.5LCSM/0.5LSMC composite is 301.61 J kg−1 under 5 T, it can be considered as a promising candidate for use in various magnetic cooling technologies at room temperature.

The large magnetocaloric effect in GdErHoCoM (M = Cr and Mn) high-entropy alloy ingots with orthorhombic structures

High-entropy alloys (HEAs) with significant magnetocaloric effects (MCEs) have attracted widespread attention due to their potential magnetic refrigeration applications over a much more comprehensive temperature range with large refrigerant capacity (RC). However, most of them are metallic glasses (MGs) with problems of limited size, resulting in the difficulty of further applications. Therefore, research on HEAs with crystalline structures and giant MCE is urgently needed. In this paper, GdErHoCoM (M = Cr and Mn) rare-earth HEA ingots with orthorhombic structures are developed, and their magnetic behavior and MCE are studied in detail. Phase investigations find that the main phase of GdErHoCoM ingots is probably (GdErHo)Co with an orthorhombic Ho3Co-type structure of a space group of Pnma. The secondary phases in GdErHoCoCr and GdErHoCoMn are body-center-cubic Cr and Mn-rich HoCo2-type phases, respectively. Magnetic investigations reveal that both ingots undergo a first-order magnetic phase transition below their respective Neel temperatures. Above their respective Neel temperatures, a second-order transition is observed. The Neel temperatures are 40 and 56 K for GdErHoCoCr and GdErHoCoMn, respectively. Additionally, the GdErHoCoCr and GdErHoCoMn ingots exhibit maximum magnetic entropy changes and RC values of 12.29 J/kg/K and 746 J/kg and 10.13 J/kg/K and 606 J/kg, respectively, under a magnetic field of 5 T. The ingots GdErHoCoM (M = Cr and Mn) show excellent MEC properties and can be manufactured easily, making them promising for magnetic refrigerant applications.

Tailoring the cryogenic magnetism and magnetocaloric effect from Zr substitution in EuTiO3 perovskite

Refrigeration in the liquid helium temperature range provides vital technological support for many scientific frontiers and engineering technologies. The considerable magnetocaloric effect (MCE) makes EuTiO3 a potential candidate for magnetic refrigeration near liquid helium temperature. More interestingly, the magnetic transition from antiferromagnetism to ferromagnetism offers the possibility to tailor the magnetism and improve the MCE of this magnetic system. In this study, the magnetic properties and MCE of EuTi0.875Zr0.125O3 were systematically investigated by first-principles calculation and experiments. The substitution of Zr induces a significant lattice expansion and alters the electronic interactions, leading to a dominance of ferromagnetism in the compound. Remarkable low-field MCE performance has been achieved attributed to the enhanced ferromagnetism and low saturation field. Under the field change of 0–1 T, the maximum magnetic entropy change (−ΔSMmax) and adiabatic temperature change (ΔTadmax) are 17.9 J kg−1 K−1 and 6.1 K, respectively. It is worth noting that the −ΔSMmax of EuTi0.875Zr0.125O3 reaches 10.3 J kg−1 K−1 for a field change of 0–0.5 T, making it one of the best magnetocaloric materials ever reported operating in the liquid helium temperature range.

Wide temperature span and giant refrigeration capacity magnetic refrigeration materials for hydrogen liquefaction

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

Enhancement of magnetocaloric effect by partial substitution of Bi in La0.60Dy0.10Sr0.30Mn(1−x)BixO3 manganites (x = 0, 0.01, 0.03, and 0.10)

In this study, the effects of Bi substitution for Mn on the magnetic and magnetocaloric properties of La0.60Dy0.10Sr0.30Mn(1−x)BixO3 manganites (x = 0, 0.01, 0.03, and 0.10) synthesized using the sol–gel method ​​were investigated. The samples x = 0, 0.01, and 0.03 had been indexed in an orthorhombic structure (space group Pnma), while sample x = 0.10 had been indexed in a hexagonal structure (space group R3c). The thermomagnetic measurements showed an increase in the Curie temperature (TC) with increasing Bi content, as well as an increase in magnetization at low temperatures. The TC values were determined as 322, 318, 327, and 360 K for x = 0, 0.01, 0.03, and 0.10 samples, respectively. Maximum magnetic entropy change (-ΔSMmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{M}^{max}$$\\end{document}) values ​​obtained from isothermal magnetization measurements showed an increase with the amount of Bi. The -ΔSMmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-\\Delta {S}_{M}^{max}$$\\end{document} value of 3.80 Jkg−1K−1 at 5 T for the x = 0 sample increased to 4.12 Jkg−1K−1 for the x = 0.10 sample with the highest Bi content. From the Arrott curves, it was observed that all samples exhibited a second-order magnetic phase transition. The obtained values of relative cooling power (RCP), which is an important factor in determining the performance of cooling material, are in the range of 282, 262, 251, and 232 Jkg−1 for x = 0, 0.01, 0.03, and 0.10, respectively.

Magnetism and magnetocaloric effects in tetragonal structure of RE5Ni2Sb (R = Er, Ho) compounds

In this work, the RE5Ni2Sb (RE = Er, Ho) compounds with tetragonal structure were successfully synthesized and the magnetism, magnetic phase transition and magnetocaloric effects were investigated. It was demonstrated that antiferromagnetic interaction undergoes a field-induced metamagnetic transition from antiferromagnetism to ferromagnetism in RE5Ni2Sb (RE = Er, Ho) under a magnetic field higher than 3 T. Moreover, the Er5Ni2Sb and Ho5Ni2Sb undergo an antiferromagnetic to paramagnetic magnetic phase transition at approximately 18 K and 25 K, and exhibit considerable magnetocaloric effects. The maximum magnetic entropy changes are 9.8 J/kg K and 10.6 J/kg K under varying magnetic fields of 0–5 T. Therefore, the large reversible MCE under low magnetic field change indicates the potential application of RE5Ni2Sb (RE = Er, Ho) in hydrogen liquefaction magnetic refrigerators. Prime Novelty StatementThis work investigates the synthesis, magnetism, and magnetothermal effects of R5Ni2Sb (R = Er, Ho) compounds. The R5Ni2Sb (R = Er, Ho) compounds have been demonstrated for the first time to have a potential application as magnetic refrigeration materials.

Estimation on magnetic entropy change and specific heat capacity through phoenomological model for Heusler melt spun ribbon of Ni47Mn40−x Si x In3 (x = 1, 2 and 3)

Abstract In this, we report the temperature-dependent magnetization [M(T)] in two distinct magnetic fields of 0.5 T and 5 T for Ni47Mn40−x Si x In3 (x = 1, 2, and 3) alloys. Using a phenomenological model and Maxwell’s thermodynamic relation, the values of the magnetic entropy change and specific heat capacity are calculated, and their values are also compared. The maximum magnetic entropy change and specific heat capacity peak values for different magnetic fields are both steadily reduced for the samples with x = 1 to 3 samples, which is followed by an increase in relative cooling power value. In comparison to 0.5 T magnetic field, the samples investigate the highest values of magnetic entropy change (3.32, 2.81, 2.01 J kg−1 K−1) and specific heat capacity (32.37, 14, 4.32 J kg−1 K−1) with a magnetic field of 5 T. According to this finding, the sample is more responsible for the magnetic field than chemical pressure.

Large reversible multicaloric effects over a broad refrigeration temperature range in Co and B co-doped Ni–Mn–Ti alloys

Solid-state refrigeration is considered a promising alternative to traditional vapor compression refrigeration technology. Researchers demonstrated that Ni–Mn–Ti alloys have a remarkable elastocaloric effect. However, the Ni–Mn–Ti alloy can only operate under a uniaxial stress field due to its antiferromagnetic austenite, which narrows its range of refrigeration temperatures. Here, we activated the magnetism of the alloy by replacing some Ni atoms with Co atoms. The Ni–Co–Mn–Ti–B alloy demonstrates a reversible maximum magnetic entropy change(ΔSm) of 24.9 J kg−1 K−1 and achieves an adiabatic temperature change of 7.8 K under a 7 T magnetic field. Additionally, we demonstrate that adding boron (0.2%) can improve the mechanical properties and cyclic stability in Ni–Mn–Ti alloys. The elastocaloric effect of 21.3 K with high cycle stability (1013 cycles) were successfully achieved in the directionally solidified (Ni35Co15Mn35Ti15)99.8B0.2 alloy. Furthermore, we have demonstrated that the magnetoelastic coupling effect can effectively extend the refrigeration temperature range. The alloys achieved large caloric effects in the temperature range of 240 K–340 K. This provides a new strategy for designing high-performance materials for wide-temperature-domain refrigeration.

Large low-field magnetocaloric performances of the ErCu1.95T0.05Si2 (T = Mn, Fe, Co and Ni) compounds

Magnetocaloric materials are at the heart of magnetic refrigeration (MR) technology. However, there is a scarcity of materials with a large magnetocaloric effect (MCE) at magnetic fields below 2 T. To address this limitation, we investigate the effect of doping in the ErCu2Si2 compound with relatively inexpensive neighboring atoms of Mn, Fe, Co, and Ni in the Cu position, respectively. The results show a significant enhancement in the MCE at low fields. Under the magnetic field change of 0–2 T, the values of maximum magnetic entropy change (−ΔSMmax) for the ErCu1.95T0.05Si2 (T = Mn, Fe, Co and Ni) compounds are 16.4 J/kg·K, 17.5 J/kg·K, 17.8 J/kg·K, and 18.6 J/kg·K, respectively. Compared to those of the parent compound ErCu2Si2, the −ΔSMmax of the ErCu1.95T0.05Si2 (T = Mn, Fe, Co and Ni) compounds exhibit enhancements of 3%, 11%, 13%, and 17%, respectively. Additionally, the magnetic transition temperatures of these doped compounds are lower than that of the parent compound ErCu2Si2, occurring below 2 K. Therefore, ErCu1.95T0.05Si2 (T = Mn, Fe, Co and Ni) compounds with large low-field MCE and negligible loss of hysteresis have the potential to serve as candidate materials for cryogenic magnetic refrigeration.