Candidates For Magnetic Refrigeration Applications Research Articles

Hysteresis behavior and magnetocaloric effect in MnNiGa[formula omitted] full-Heusler alloy

In this manuscript, we studied the magnetic, magnetocaloric, and hysteresis properties of the MnNiGa2 full-Heusler alloy using mean-field theory and first-principles calculations. Initially, we employed the GGA+U method to investigate the structural characteristics of the alloy. Our findings indicated that the ferromagnetic state, with an optimal lattice parameter of 5.88 Å, was the most stable compared to the antiferromagnetic states. Additionally, the exchange interactions, defined as the Hamiltonian parameters of the studied system, were calculated and used in the mean-field approximation. The second-order transition at a Curie temperature of Tc = 373 K, previously revealed experimentally, has been confirmed. Furthermore, the alloy exhibited a relative cooling power (RCP) of 260.43 J/kg and a magnetocaloric effect of 10.34 J/kg.K at an applied magnetic field of 1.4 T. These results suggest that MnNiGa2 is a promising candidate for magnetic refrigeration applications.

Mechanically strong and room-temperature magnetocaloric monolayer VSi2N4 semiconductor

In the realm of emerging two-dimensional MoSi2N4 family, the majority of research endeavors gravitate toward their versatile physical properties, while their magnetocaloric effect (MCE) for the potential refrigeration application remains uncharted. Here, we comprehensively explore the magnetic, electronic, mechanical, and magnetocaloric properties of monolayer VA2Z4 (A = Si, Ge; Z = N, P, As) family by multiscale simulations, revealing that monolayer VSi2N4 semiconductor is mechanically strong and exhibits room-temperature MCE. The nonlinear elastic response of VSi2N4 unveils strong mechanical properties, featuring a substantial in-plane Young's modulus (E2D∼ 350 N/m) and a high strength of 40.8 N/m, comparable to that of graphene. Monolayer VSi2N4 exhibits a room-temperature MCE with an extensive refrigeration temperature range up to 20 K. Furthermore, applying biaxial strain can significantly improve the maximum magnetic entropy change (−ΔSMmax) and maximum adiabatic temperature change (ΔTadmax) by 80.9% and 197.3%, respectively. Room-temperature MCE with wide working temperature and mechanical robustness make monolayer VSi2N4 an appealing candidate for magnetic refrigeration applications over large temperature range. These findings offer fresh insights for advancing the development of magnetic cooling in small-sized systems.

A comparative study of magnetic behaviours in bulk and ribbon samples of PrMn2Ge2 compound

The magnetic properties of PrMn2Ge2 samples in both the as-cast bulk and melt-spun ribbon forms have been investigated in detail by a comprehensive set of x-ray and neutron powder diffraction, magnetic and heat capacity measurements and corresponding sets of data analyses. Thermal expansion measurements indicate the presence of magnetoelastic coupling effects around all transition temperatures in the bulk sample. The bulk modulus K0 = 42.0 GPa and its first derivative K0’ = 18.7 have been derived from the pressure-volume data. The Curie temperature from the intralayer antiferromagnetism (AFl) of PrMn2Ge2 to a canted spin structure (Fmc) is TCinter = 332 K for the bulk sample, decreasing to TCinter = 320 K for the ribbon sample. The critical components γ, β and δ of this second order magnetic transition as determined from Kouvel-Fisher analyses, indicate long range magnetic interactions around TCinter. Based on these critical exponents the magnetization, field and temperature data around TCinter collapse onto two curves obeying the single scaling equation M(H,ε)=εβf±(Hεβ+γ). The Debye temperatures and the density of states at the Fermi level are θD=306K and N(EF)=3.47state/eVatom for the bulk sample and θD=320K and (EF)=2.18state/eVatom for the ribbon sample with the nuclear specific heat coefficient for bulk PrMn2Ge2 derived from the splitting of the nuclear hyperfine levels as CN = 517 mJ mol−1 K−1. With a field change of ΔB = 5 T, the maximum values of the magnetic entropy changes -ΔSmax in the region around TCinter are -ΔSmax = 3.00 J/kg K and 2.35 J/kg K for the bulk and ribbon samples respectively, while the relative cooling power (RCP) for the ribbon-spun sample, RCP = 135.9 J/kg, is significantly higher than the value of RCP = 116.6 J/kg for the bulk sample. These findings indicate that PrMn2Ge2 could be a promising candidate for magnetic refrigeration applications in the room temperature region.

Ab-initio and Monte Carlo studies of magnetic and magnetocaloric properties of antiperovskite Mn[formula omitted]AlN

In this study, we systematically investigate the electronic, magnetic, and magnetocaloric properties of Mn3AlN antiperovskite. This system is examined through first-principles computations using density functional theory (DFT) and Monte Carlo (MC) simulations. Based on the density of state and band structure, it is found that Mn3AlN behaves as a ferromagnetic metallic material. Additionally, we calculate the magnetic anisotropy and exchange interactions, which are parameters of the Hamiltonian, and incorporate them into the MC simulation. Concerning the magnetic properties, the critical temperature of the antiperovskite (Tc= 811 K) is almost similar to the experimental value (Tc= 818 K). Furthermore, we also investigate the magnetocaloric properties and find that the relative cooling power (RCP) values and maximum entropy change for a magnetic field strength of 5 T are 93.96 J/kg and 12.55 J/kg K, respectively. These results suggest that Mn3AlN is a promising candidate for magnetic refrigeration applications.

Enhancement of the thermal conductivity of a near room temperature magnetocaloric composite using graphene-like hybrid nanosheets derived from organic waste

Polymer matrix composites, fabricated to counter the inherent brittleness of magnetocaloric Heusler alloys, suffer from low thermal conductivity. Here, we demonstrate a low-cost, scalable route towards developing thermally conductive, mechanically robust near-room-temperature magnetocaloric composites by incorporating graphene-like hybrid nanostructures chemically synthesized from discarded sugarcane. Micron-sized particles obtained by manually grinding Ni50.2Mn36.7Sn13 ribbons possessing a strong magnetostructural transformation near room-temperature were chosen as the active magnetocaloric fillers. Both the functional fillers were incorporated into a polysulfone matrix by solution casting. Large values of isothermal entropy change ∼ 0.43 and -0.46 J/kg.K were observed for a ΔH = 2T, driven by two successive first and second-order transformations within the alloy fillers. Additionally, an enhanced value of the in-plane thermal conductivity ∼ 3.06 ± 0.4 W/m.K was observed in the composites owing to the formation of efficient thermal bridges/pathways by the graphene-like hybrid nanostructures, rendering them promising candidates for magnetic refrigeration applications.

Magnetic and Magnetocaloric Properties of Nano- and Polycrystalline Bulk Manganites La0.7Ba(0.3−x)CaxMnO3 (x ≤ 0.25)

Here we report the synthesis and investigation of bulk and nano-sized La0.7Ba0.3−xCaxMnO3 (x = 0, 0.15, 0.2 and 0.25) compounds that are promising candidates for magnetic refrigeration applications. We compare the structural and magnetic properties of bulk and nano-scale polycrystalline La0.7Ba0.3−xCaxMnO3 for potential use in magnetic cooling systems. Solid-state reactions were implemented for bulk materials, while the sol–gel method was used for nano-sized particles. Structurally and morphologically, the samples were investigated by X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). Oxygen stoichiometry was investigated by iodometry. Bulk compounds exhibit oxygen deficiency, while nano-sized particles show excess oxygen. Critical magnetic behavior was revealed for all samples using the modified Arrott plot (MAP) method and confirmed by the Kouvel–Fisher (KF) method. The bulk polycrystalline compound behavior was better described by the tricritical field model, while the nanocrystalline samples were governed by the mean-field model. Resistivity in bulk material showed a peak at a temperature Tp1 attributed to grain boundary conditions and at Tp2 associated with a Curie temperature of Tc. Parent polycrystalline sample La0.7Ba0.3MnO3 has Tc at 340 K. Substitution of x = 0.15 of Ca brings Tc to 308 K, and x = 0.2 brings it to 279 K. Nanocrystalline samples exhibit a very wide effective temperature range in the magnetocaloric effect, up to 100 K. Bulk compounds exhibit a high and sharp peak in magnetic entropy change, up to 7 J/kgK at 4 T at Tc for x = 0.25. To compare the magnetocaloric performances of the studied compounds, both relative cooling power (RCP) and temperature-averaged entropy change (TEC) figures of merit were used. RCP is comparable for bulk polycrystalline and nano-sized samples of the same substitution level, while TEC shows a large difference between the two systems. The combination of bulk and nanocrystalline materials can contribute to the effectiveness and improvement of magnetocaloric materials.

Anisotropic magnetic property, magnetostriction, and giant magnetocaloric effect with plateau behavior in TbMn2Ge2 single crystal

The ternary RMn2Ge2 (R = rare earth) intermetallic compounds have attracted great attention due to their interesting magnetic behaviors and magnetotransport responses. Here, we reported our observation of anisotropic magnetic property, magnetostriction, and magnetocaloric effect (MCE) in TbMn2Ge2 single crystal. Below the transition temperature of Tb magnetic sublattices (T_{{text{C}}}^{{{text{Tb}}}} ~ 95 K), strong Ising-like magnetocrystalline anisotropy is observed with an out-of-plane ferromagnetic moments 5.98 μB/f.u. along the easy c axis, which is two orders of magnitude larger than that of field along a axis. Above T_{{text{C}}}^{{{text{Tb}}}}, a field-induced metamagnetic transition is observed from the spin-flip of Mn sublattices. During this transition, remarkable magnetostriction effect is observed, indicating of strong spin–lattice coupling. The responses of Tb and Mn sublattices to the magnetic field generate a giant magnetic entropy change (- Delta S_{M}) and large values of relative cooling power (RCP) and temperature-averaged entropy change (TEC). The calculated maximum magnetic entropy change (- Delta S_{M}^{max }), RCP, and TEC(10) with magnetic field change of 7 T along c axis reach 24.02 J kg−1 K−1, 378.4 J kg−1, and 21.39 J kg−1 K−1 near T_{{text{C}}}^{{{text{Tb}}}}, which is the largest among RMn2Ge2 families. More importantly, this giant MCE shows plateau behavior with wide window temperatures from 93 to 108 K, making it be an attractive candidate for magnetic refrigeration applications.

Microstructure evolution and accelerated magnetocaloric phase formation of LaFe13.1Co0.7Si1.4 alloy by forging deformation at room temperature

In order to improve the preparation process and practical process of magnetic refrigerant, a method of accelerating phase formation by cold compression plastic deformation at room temperature is proposed. To determine the significance of this method, the grain structure, phase composition and magneto-thermal effects of LaFe13.1Co0.7Si1.4 alloy were systematically studied. The results show that with the increase of compression ratio, the number of grains per unit volume increases and the grain size tends to be uniform. Compared with the uncompressed sample, the proportion of magnetothermal phase in the pre-compressed samples increases after annealing under the same conditions. When the deformation is 40%, the ratio of 1:13 phase in pre-deformed sample after 1 day annealing is 72 vol%, which is significantly better than that of the undeformed sample. After annealing for 3 days, the Curie temperature (TC) of 40% pre-deformed LaFe13.1Co0.7Si1.4 samples is 330 K, and the magnetic entropy changes to − 4.70 J/kg K and − 5.42 J/kg K under 2 T and 3 T magnetic fields, respectively. The appropriate Curie temperature and value of ∆SM make it an attractive potential candidate for magnetic refrigeration application at room or even high temperature.

Magnetic structure, magneto-caloric properties and magnetic critical behaviours of LaMn2Ge2 compounds

The structural and magnetic properties of LaMn2Ge2 compound in both the as-cast bulk and melt-spun ribbon forms have been investigated by a comprehensive set of x-ray/neutron powder diffraction, magnetic and heat capacity measurements as well as corresponding sets of data analyses. Our neutron diffraction study reveals that with decreasing temperature the magnetic state of bulk LaMn2Ge2 changes first from paramagnetic to incommensurate antiferromagnetism AFfs at TN ~ 430 K, and then gives way to incommensurate canted ferromagnetism Fmi below TC ∼ 320 K. No noticeable magnetoelastic effect was detected in the temperature dependence of lattice parameters derived from the refinement of the neutron diffraction patterns over the temperature range ~ 5–460 K. Detailed analyses of the magnetic data indicate that the magnetic phase transition around the ferromagnetic transition (TC ∼ 320 K) is second order. Under field changes of 2 T and 5 T, the maximum values of magnetic entropy change around the ferromagnetic transition respectively reach -ΔSmax = 1.65 J/kg K and -ΔSmax = 3.26 J/kg K for the bulk sample, compared with -ΔSmax = 1.21 J/kg K and -ΔSmax = 2.60 J/kg K, for the ribbon sample. The magnetic phase transition around TC has been investigated by Kouvel-Fisher analysis and the Modified Arrott Plot method with the critical exponent values indicating that the magnetic interactions in LaMn2Ge2 are long range. Moreover, it was found that the field- and temperature- magnetisation data around TC collapse onto two curves obeying the single scaling equation M(H,ε) = εβf ± (H/εβ+γ) for both the bulk and ribbon samples. With a field change of ΔB = 5 T and ΔB = 8 T, the relative cooling power for bulk sample around 320 K is derived to be RCP ~ 115 J/kg and RCP ~ 199 J/kg, respectively. These findings indicate that LaMn2Ge2 could be a promising candidate for magnetic refrigeration applications in the room temperature region.

Experimental and theoretical study of magnetic and magnetocaloric properties of the lacunar La0.8□0.2MnO2.8 compound: Bean-Rodbell model

In this paper, our research focuses on the correlation between structural and magnetic properties of the lacunar polycrystalline La0.8□0.2MnO2.8. The structural analysis proves a coexistence between R-3c and Pnma crystallographic structure. The analysis of the hysteresis loop shows that La0.8□0.2MnO2.8 sample is a Ferromagnetic soft material with an antiparallel magnetic coupled for both phases (Pnma and R-3c). Using servals theoretical approaches, the anisotropic parameters were estimated. The magnetocaloric properties were also investigated. A good result of the relative value of cooling power has been achieved (60% of that of Gd at 2 T) indicating that the material is a potential candidate for magnetic refrigeration application. The use of the Bean-Rodbell model based on the mean field theory allowed us to examine the nature of the magnetic transition and to calculate the magnetic and magnetocaloric properties with good accuracy. Moreover, within the framework of the mean-field theory, the spontaneous magnetization values MSp were estimated using the magnetic entropy change curves (-ΔS (M)).

Room-temperature large magnetocaloric, electronic and magnetic properties in La0.75Sr0.25MnO3 manganite: Ab initio calculations and Monte Carlo simulations

By using the Ab initio and Monte Carlo calculations, we have studied the magnetism of the crystalline La0.75Sr0.25MnO3 perovskite. The ferromagnetic phase of La0.75Sr0.25MnO3 is half-metallic, which is important in the relation to the colossal magnetoresistance properties of this compound. The total magnetic moment and the exchange couplings deduced from ab initio calculations lead, by using Monte Carlo simulations, to a quantitative agreement with the experimental transition temperatures. The maximum magnetic entropy change and the specific heat are found to be 9.23 J K−1 kg −1 and 191 J mol −1 K−1, respectively for H=6 T. Our results suggest that this material a promising candidate for magnetic refrigeration application near to room temperature at moderate fields.

Correlation between particle size and magnetic properties in soft-milled Ni45Co5Mn34In16 powders

The effect of microstructural defects induced by mechanical milling has been studied in a Ni–Mn–In–Co metamagnetic shape memory alloy. The martensitic transformation and Curie temperatures do not change with grinding, thus pointing out to a null variation of long range atomic order as a consequence of the deformation. Nevertheless, the enthalpy change of the martensitic transformation highly decreases. This, and the large thermal stabilization of the martensite (with shifts on the temperature of the first reverse martensitic transformation up to 60 K), indicate the presence of a huge amount of internal stresses and microstructural defects in the obtained micro-particles. The presence of such defects considerably affects the saturation magnetization in austenite whereas almost no effect is observed in martensite. The magnetocaloric effect has been evaluated in samples with three different particle sizes. In spite of the MCE value is lower than in the bulk, the broader temperature range for the martensitic transformation in the powders makes the relative cooling power be comparable to that in the bulk. The as-milled micro-particles can be then considered as good preliminary candidates for magnetic refrigeration applications at the microscale.

Magnetic properties, magnetocaloric effect and cooling performance of AlFe[formula omitted]B[formula omitted] compound: Ab initio, Monte Carlo and numerical modeling study

The structural and electronic properties of AlFe2B2 compound have been investigated using ab initio calculations based on the Density Functional Theory (DFT) as implemented in the WIEN2k code. The magnetic exchange couplings have been calculated using SPRKKR code. Then, the magnetic and magnetocaloric properties have been studied using Monte Carlo simulation. The results confirm that the AlFe2B2 compound is ferromagnetic. In addition, AlFe2B2 exhibits a second-order magnetic phase transition at 290 K. For the magnetic field change of 0–5 T, the maximum values of the magnetic entropy change (-ΔSm), the adiabatic temperature change (ΔTad) and the relative cooling power (RCP) for AlFe2B2 are 7.65 J.kg−1, 3.84 K and 210 J.K−1 respectively. A 1D model of the AMR system has been developed. The model has been used to access the performance of AlFe2B2 in a packed-bed AMR. The results confirm that, the AlFe2B2 compound could be a promising candidate for magnetic refrigeration applications.

The effect of rare-earth Gd-substitution on the structural, magnetic and specific heat properties in orthorhombic DyMnO3 ceramics

The acrylamide polymer gel template method has been adopted to synthesize single phase Dy1–xGdxMnO3 (DGMO, x= 0, 0.05, 0.1, 0.15, 0.2) ceramics. The Rietveld refinement of x-ray diffraction patterns recorded at room temperature suggests that DGMO ceramics are stabilized in an orthorhombic crystal structure with a Pnma space group. Gd3+ cations play an important role in stabilizing the orthorhombic phase and the unit cell volume increases with x. We report the phonon spectra of pure and Gd-substituted DyMnO3 (DMO) and their mode assignments. Raman modes are softened with x due to the relaxation in the stiffness constants upon the increase in the volume of the unit cell. The magnetic transition temperatures corresponding to TN(Dy) and Tlock decrease with the increase in Gd concentration as inferred from the temperature dependent magnetization data (M–T curve). The magnetization value increases below TN(Dy) with the increase in the Gd concentration as observed from the M–T plot. The magnetic hysteresis loop is fitted to extract ferromagnetic and antiferromagnetic/paramagnetic contributions for each composition x. Fittings of M–H loops indicate the increase in the magnetic contribution below TN(Dy) upon increasing the Gd dopant concentrations, while that decreases above TN(Dy). The temperature dependent specific heat data identifies these magnetic transition temperatures TN(Dy), Tlock and TN(Mn). Furthermore, magnetic field dependencies on TN(Dy), Tlock and TN(Mn) are studied in an elaborate manner. Both DMO and DGMO samples are found to be viable candidates for magnetic refrigeration applications in cryogenic temperature region.

Phenomenological Modeling of Magnetocaloric Properties in 0.75La0.6Ca0.4MnO3/0.25La0.6Sr0.4MnO3 Nanocomposite Manganite

In the current research work, a phenomenological model is applied to describe the magnetocaloric effect (MCE) of the two phases 0.75 La0.6Ca0.4MnO3/0.25 La0.6Sr0.4MnO3 composite system. Based on this model, the values of the magnetocaloric properties are predicted from the calculation of magnetization as a function of temperature under different external magnetic fields. A significant MCE is obtained over a large range of temperature compared to those observed in the mother compounds, La0.6Ca0.4MnO3 and La0.6Sr0.4MnO3, making of this material considered as a promising candidate for magnetic refrigeration applications in moderate magnetic fields near room temperature. The results are then compared to those obtained experimentally in our previous work. The excellent agreement observed between both data proves the validity of the adopted model in the estimation of the MCE properties of material under investigation.

Synthesis of La0.5Ca0.5−x□xMnO3 nanocrystalline manganites by sucrose assisted auto combustion route and study of their structural, magnetic and magnetocaloric properties

Perovskite manganite La0.5Ca0.5-x xMnO3 (LCMO) nanomaterials were elaborated using the sucrose modified auto combustion method. Rietveld refinements of the X-ray diffraction patterns of the crystalline structure confirm a single-phase orthorhombic state with Pbnm space group (No. 62). The Ca-vacancies were voluntarily created in the LCMO structure in order to study their influence on the magnetic behaviour in the system. The magnetic susceptibility was found to be highly enhanced in the sample with Ca-vacancies. Paramagnetic-to-ferromagnetic phase transition was evidenced in both samples around 254 K. This transition is, characterized by a drastic jump of the susceptibility in the sample with Ca-vacancies. The maximum of entropy change, observed for both compounds at magnetic field of 6T was 2.30 J kg-1K-1 and 2.70 J kg-1K-1 for the parent compound and the lacunar one respectively. The magnetocaloric adiabatic temperature change value calculated by indirect method was 5.6 K and 5.2 K for the non-lacunar and Ca-vacancy compound, respectively. The Ca-lacunar La0.5Ca0.5-x xMnO3 (x=0.05) reported in this work demonstrated overall enhancement of the magnetocaloric effect over the LCMO. The technique used to elaborate LCMO materials was beneficial to enhance the magnetocaloric effect and magnetic behaviour. Therefore, we conclude that this less costly environmentally friendly system can be considered as more advantageous candidate for magnetic refrigeration applications then the commonly Gd-based compounds.

Magnetocaloric effect near room temperature in quintenary and sextenary Heusler alloys

An inverse magnetocaloric effect is studied in Ni2Mn1+xX1−x-type Heusler alloys. Principally known for their shape-memory properties, these alloys also exhibit significant entropy and temperature changes (ΔS and ΔTAd, respectively) under adiabatic conditions when a modest magnetic field is applied. We investigated the impact on magnetocaloric properties of introducing substantial chemical disorder on the X-site (X=Si,Ga,In), of replacing Ni with nonmagnetic Ag, and of replacing a small amount of Mn with Gd. While a reduction in ΔS is observed in the first two cases, we observe a significant enhancement of ΔS when a small amount of Gd is substituted for Mn. A thermodynamic analysis was conducted using magnetization and heat capacity data to estimate adiabatic temperature changes in the range of ΔTAd≃ −1 to −3 K for a 5 T magnetic field. Several alloys characterized in this study exhibit these respectable ΔTAd values near room temperature, making them potentially viable candidates for magnetic refrigeration applications.

Magnetocaloric effect, corrosion and mechanical properties of Mn1.05Fe0.9P0.5Si0.5Cux alloys

To enhance the corrosion resistance and mechanical properties of magnetocaloric materials in the application of magnetic refrigeration, Cu was introduced into (Mn,Fe)2(P,Si) system. A series of Mn1.05Fe0.9P0.5Si0.5Cux (x = 0, 0.05, 0.10 and 0.15) alloys were prepared by arc-melting and subsequent copper mold suction casting method. The results show that Mn1.05Fe0.9P0.5Si0.5Cux alloys crystallized into a typical Fe2P-type main phase with hexagonal structure. In microstructure, most of Cu segregated at the grain boundaries of main phase, while a small amount of Cu entered the Fe2P structure. The precipitation of pure copper phase at the grain boundaries contribute to the improvement of corrosion and mechanical properties. The Curie temperature of Mn1.05Fe0.9P0.5Si0.5Cux alloys can be continuously tuned from 321 K to 248 K with the increase of copper contents, while the magnetic entropy changes slightly reduced. In comparison with Mn1.05Fe0.9P0.5Si0.5, the corrosion potential of Mn1.05Fe0.9P0.5Si0.5Cu0.15 increases from −0.3932 V to −0.2747 V, while the corrosion current density decreases by 63.2%, which indicates a significantly improved corrosion resistance. The nano-indentation tests also indicate that the incorporation of Cu can effectively improve the mechanical performance of these alloys. All results indicate that Mn1.05Fe0.9P0.5Si0.5Cux alloys are promising candidates for magnetic refrigeration applications.

Structural, magnetic, critical behavior and phenomenological investigation of magnetocaloric properties of La0.6Ca0.4−xSrxMnO3 perovskite

Structural, magnetic, critical behavior and magnetocaloric properties of La0.6Ca0.4−xSrxMnO3 (x = 0.0, 0.1 and 0.4) compounds have been investigated. Rietveld refinement of the X-ray diffraction patterns indicates that our samples are pure single phase adopting the rhombohedral structure (R-3c) for x = 0.0 and the orthorombic structure (Pbnm) for x = 0.1 and 0.4. Temperature dependence of magnetization curves exhibit a second order paramagnetic (PM)/ferromagnetic (FM) phase transition at Curie temperature Tc. The critical behavior has been determined through the isothermal magnetization measurements around the critical temperature Tc by means of various techniques such as modified Arrott plot (MAP), Kouvel-Fisher (KF) method and critical isotherm analysis (CIA). The results are fully satisfactory to the requirements of the Widom scaling relation and the universal scaling hypothesis confirming their accuracy. A phenomenological model is applied to describe the magnetocaloric effect (MCE) behavior of compounds under investigation. At $$ \mu_{0} H = 5T $$ , the obtained RCP values stand for about 98, 77 and 68% of that observed in pure Gd for x = 0.0, 0.1 and 0.4, respectively, making of these materials considered as promising candidates for magnetic refrigeration applications near room temperature. By analyzing the field dependence of the magnetic entropy change data as well as the relative cooling power, it was possible to evaluate the critical exponent values which were found not only agree with those deduced from (MAP), (KF) and (CIA) methods, but they also obey the scaling theory. Our findings confirm the good correlation between the critical behavior and the MCE properties in manganite systems.

Magnetocaloric effect in Gd60Al25(NiCo)15 bulk metallic glass

Magnetic cooling technology is a very promising alternative to conventional vapor compression refrigeration systems. Searching for suitable magnetocaloric materials with improved properties is a key issue in this field. In this work, we report thermal, magnetic and magnetocaloric properties of the Gd60Al25(NiCo)15 bulk metallic glass. A completely amorphous sample of 3 mm in diameter is successfully fabricated by a vacuum suction casting method. The alloy demonstrates the distinct glass transition and near-eutectic melting. Magnetic measurements reveal ferromagnetic ordering in the BMG at about 91 K. We have found a field-induced magnetic transition in the glass, which provides a table-like behavior for the magnetic entropy changes. Due to this metamagnetic effect, the BMG demonstrates excellent magnetocaloric effect over a wide temperature range. The values of relative cooling power (RCP) and the full width of half maximum of magnetic entropy change (ΔTFWHM) under a magnetic field of 5 T are 890 J × kg−1 and 141 K, respectively. All that makes this glass a promising candidate for magnetic refrigeration applications working at liquid‑nitrogen temperatures.