Relative Cooling Power RCP Research Articles

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.

Magnetothermal Properties and Magnetocaloric Effect in the 3d Ferromagnetic Elements: Fe, Co, and Ni

We present a calculation of magnetothermal properties and magnetocaloric effect (MCE) for the ferromagnetic elements: Fe, Co, and Ni. In particular, we calculated the temperature and field dependences of magnetization, heat capacity, entropy, isothermal entropy change Delta {S}_{m}, adiabatic temperature change ΔTad, and the two figures-of-merit: the relative cooling powers RCP(S) and RCP(T). We have used the mean-field theory in calculating the magnetization, magnetic heat capacity, and magnetic entropy. The lattice and electronic contributions to the total heat capacity and entropy were calculated using standard relations to subsequently calculate Delta {T}_{ad}. Those contributions depend on the Debye temperature ϴD and the coefficient of the electronic heat capacity γe respectively. The Maxwell relation is used to calculate Delta {S}_{m} and Delta {T}_{ad}. As an example of our results, the maximum Delta {S}_{m} for the three elements, in 6 T, is between 0.17 to 0.36 J/mol K and the maximum Delta {T}_{ad} mathrm{} is between 0.46 to 1.5 K/T for the same field change. The relative cooling power RCP(S) is in the 15–36 J/mol range for the three elements in a 6 T field. Also, the relative cooling power, RCP (T), is in the 162–1044 {K}^{2} range for the same field. For Fe and Co the RCP (T) per Tesla values, i.e., 139 and 174 {K}^{2}/T respectively are comparable to that of Gd and other Gd-based magnetocaloric materials. The behavior of the magnetization, magnetic heat capacity, and magnetic entropy shows that the phase transition in these three elements is of the second order. The universal curve and Arrott plots further support this conclusion.

Structural, magnetic and magnetocaloric properties of Laves phase (Gd,Sm)Co[formula omitted] compound

In the present work, the structural, magnetic, and magnetocaloric properties of the intermetallic Gd1−xSmxCo2 (x=0.5,0.6 and 0.7) compounds have been systematically studied. Samples were prepared by arc melting under high pure argon and homogenized at 800 K to minimize the impurity phases. X-ray diffraction (XRD) coupled with Rietveld analysis has shown that all samples crystallize in the cubic MgCu2-type structure (Space group Fd-3 m). Refinement results show that the unit cell parameter increases with increasing Sm content. The magnetic measurement reveals that the Sm content reduces the Curie temperature TC from 404 (for x=0) to 263 K (for x=0.7). The magnetic entropy change of the samples as function of temperature and applied magnetic field were calculated from the isothermal magnetization curves using Maxwell relation. The relative cooling power RCP and the temperature-averaged entropy change (TEC) have been reported. Furthermore, the magnetocaloric behavior is studied using the scaling laws and the phenomenological universal curve.

Magnetocaloric Effect in R6Fe23: R = Dy, Ho, Er, and Tm

We present a mean field study on the R6Fe23 system, where R = Dy, Ho, Er, and Tm, to calculate the magnetization, magnetic heat capacity, and the magnetocaloric effect (MCE) (isothermal entropy change (ΔSm) and the adiabatic temperature change (ΔTad)) for different field changes up to 5 T and at temperatures ranging from 0 to 600 K. The maximum ΔSm, using the trapezoidal method, for the R6Fe23 system is in the range 4.9–9.8 J/K mol, and the maximum ΔTad is in the range 9.56–15.17 K for a field change ΔH = 5 T. The largest ΔSm and largest ΔTad are found for Tm6Fe23 to be 9.8 J/K mol and 15.17 K at Curie temperature Tc = 489 K, for ΔH = 5 T. The relative cooling power RCP(S) is in the range 148–560 J/mol for ΔH = 5 T, which is comparable to that of bench-mark materials, e.g., Gd. Also, the RCP based on the adiabatic temperature change, RCP(T) is in the range 449–1092 K2 for ΔH = 5 T, which is comparable also to that of bench-mark materials, e.g., Gd. We investigated the type of phase transition in the light of universal curves, Arrott plots, and the behavior of the magnetic moment, magnetic heat capacity, and MCE (ΔSm, ΔTad), which confirm that the type of phase transition at Tc of this system is second-order phase transition (SOPT). A calculation of some critical exponents adds more evidence that the MFT is fairly suitable to handle the aforementioned properties in the studied systems.

Effect of Ni Substitution on the Structural, Magnetic, and Electronic Structure Properties of Gd0.4Tb0.6(Co1-xNix)2 Compounds.

The comprehensive research of magnetic and electronic structure properties of the new class of Gd0.4Tb0.6(Co1-xNix)2 compounds, crystallizing in the cubic Laves phase (C15), is reported. The magnetic study was completed with electrical resistivity and electronic structure investigations. The analysis of Arrott plots supplemented by a study of temperature dependency of Landau coefficients revealed that all compounds undergo a magnetic phase transition of the second type. Based on magnetic isotherms, magnetic entropy change (ΔSM) was determined for many values of the magnetic field change (μ0H), which varied from 0.1 to 7 T. For each compound, the ΔSM had a maximum around the Curie temperature. Both values of the |ΔSMmax| and relative cooling power RCP parameters increased with increasing nickel content. It is shown that structural disorder upon Co/Ni substitution influences some magnetic parameters. The magnetic moment values of Co atoms determined from different methods are quantitatively consistent. From the M(T) dependency, the exchange integrals JRR, JRT, and JTT between rare-earths (R) and transition metal (T) moments were evaluated within the mean-field theory (MFT) approach. The experimental study of the electronic structure performed with the use of the X-ray photoelectron spectroscopy (XPS) was completed by calculations using the full-potential linearized augmented plane waves (FP-LAPW) method based on the density functional theory (DFT). The calculations explained experimentally observed changes in the XPS valence band spectra upon the Ni/Co substitution.

Magnetic properties and magnetocaloric effect of R2Fe14B compounds with R = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho and High-Magnetic field phase transitions in the compounds with R = Gd, Dy

The temperature and field dependences of the: magnetization, magnetic specific heat and magnetic entropy of the R2Fe14B compounds, are studied using the mean-field two-sublattice model, where R = Y, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and B is boron. The isothermal entropy change ΔSm and the adiabatic temperature change ΔTad are calculated, for magnetic fields ≤ 5 T, by a Maxwell’s relation and a well-known integration involving the total heat capacity. The temperature range for these calculations is up to 700 K. Direct magnetocaloric effect (MCE), in all compounds, is present with maximum ΔSm and ΔTad in the range of 0.9–6.8 J/mol. K and 1.5–7.7 K, respectively, for a magnetic field change in the range of 1–5 T. The relative cooling power RCP(S) is in the range of 196–526 J/ kg. Ferrimagnetic compounds show both direct and small inverse MCE. It is found that Pr2Fe14B has the highest ΔSm of 6.8 J/mol. K and the largest ΔTad of 7.7 K at a magnetic field change of 5 T. The magnetization curves are calculated for Dy2Fe14B for temperatures in the range of 30–200 K and for Gd2Fe14B from 46 to 400 K for magnetic fields up to 300 T. It is found that these two compounds exhibit ferrimagnetic to ferromagnetic first-order phase transitions. Belov -Arrott plots, for these two compounds, show S-shaped feature which supports the occurrence of a first-order phase transition.

Influence of rare-earth doping on the structural and magnetic properties of orthoferrite La0.50R0.50FeO3 ceramics obtained under high pressure

Studies on the impact of co-doping on the structural, magnetic, and magnetocaloric properties of LaFeO3 orthoferrite-based compounds with partial isovalent substitution of La3+ by rare-earth (R) ions have been carried out. Their functional properties have been experimentally and theoretically investigated by X-ray diffraction analysis, differential scanning calorimetry, and magnetic methods as well as a semiempirical approach. The La0.50R0.50FeO3 (R = Nd, Eu, Gd, Dy, Er) ceramics have been taken as a basis and prepared by a solid-state reaction method under cold-pressing at high pressure (P = 4 GPa). The temperature dependences of the magnetization and magnetocaloric characteristics of the La0.50R0.50FeO3 orthoferrites for the whole series of substitutions from R = Ce to Lu have been calculated within the framework of the semiempirical model, assuming linearity of its parameters depending on the R cation radius. The magnetic entropy change ΔSM, relative cooling power RCP, and specific heat capacity ΔCP,H have thereby been obtained. It has been shown that the La0.50Ce0.50FeO3 composition has the highest magnetocaloric parameters with the lowest Néel temperature TN. As the R cation radius decreases, the chemical pressure increases, leading to a decrease in the magnetocaloric characteristics and an increase in TN. This is due to both a size effect of the crystallites and structural distortions. The obtained results show the potential practical applications of orthoferrite-based materials with controlled magnetocaloric effect and phase transition temperature.

Thermodynamic properties and magnetocaloric effect of a graphdiyne bilayer with RKKY interaction

Based on the Monte Carlo method, a ferromagnetic mixed spin-3/2 and spin-5/2 Ising model is extended to research the thermodynamic and magnetocaloric properties of the graphdiyne bilayer under the presence of the external magnetic field. The results of the finite-size effect show that the thickness of the nonmagnetic layers and the total number of the atoms have the significant influence on the studied quantities including magnetization, susceptibility, internal energy, specific heat, magnetic entropy, and magnetic entropy change. In addition, the maximum of the magnetic entropy change -ΔSm can be improved by increasing the exchange interaction between atoms b in the bottom magnetic surface Jb/Ja and adding the nonmagnetic layers L. We also obtain the relative cooling power RCP under the change of the external field Δh/Ja.

Comparative study on the effect of synthesis route on the structural, magnetic, and magnetocaloric properties of La0 .5Ca0.5Mn0.95V0.05O3 manganite

ABSTRACT The influence of the synthesis method on structural, magnetic and magnetocaloric properties of the La0.5Ca0.5Mn0.95V0.05O3 compound has been investigated. The compound was prepared by glycine nitrate process (GNP) and compared to counterparts obtained with solid-state route (S-S) and ball milling (B-M). The structural analysis shows a pure and single-orthorhombic crystalline phase for the GNP compound. A secondary phase LaVO4 was detected for S-S and B-M samples. From magnetization versus temperature analysis, different magnetic behaviors were distinguished when moving from one technique to another. The nature of transition was determined and a crossover from second order to first-order magnetic transition was observed with the decrease of crystallite size. Landau theory was performed to confirm the order of magnetic transition of the sample consistent with the Banerjee criterion. The magnetic entropy change (ΔSm) and the relative cooling power RCP, which decreased by reducing the particle size, were calculated.

Experimental and theoretical analysis of magnetocaloric behavior ofDy1−xErxNi2intermetallics(x=0.25,0.5,0.75)and their composites for low-temperature refrigerators performing an Ericsson cycle

In the present work, the structural, magnetic, and thermodynamic properties of ${\mathrm{Dy}}_{1\ensuremath{-}x}{\mathrm{Er}}_{x}{\mathrm{Ni}}_{2}$ $(x=0.25,\phantom{\rule{0.16em}{0ex}}0.5,\phantom{\rule{0.16em}{0ex}}0.75)$ Laves-phase intermetallics, being continuous solid solutions in the ${\mathrm{DyNi}}_{2}\text{\ensuremath{-}}{\mathrm{ErNi}}_{2}$ system, synthesized by arc melting, are experimentally studied and analyzed in accordance with mutual substitution within the rare-earth sublattice. The existence of Laves-phase superstructure (space group $F\overline{4}3m$) in the substituted ${\mathrm{Dy}}_{1\ensuremath{-}x}{\mathrm{Er}}_{x}{\mathrm{Ni}}_{2}$ compounds was found by x-ray diffraction analysis. Low-temperature magnetic studies showed the ferromagnetic behavior of the compounds; their Curie temperatures correlate with the erbium content; namely, they decrease from 16.8 K for ${\mathrm{Dy}}_{0.75}{\mathrm{Er}}_{0.25}{\mathrm{Ni}}_{2}$ to 10.0 K for ${\mathrm{Dy}}_{0.25}{\mathrm{Er}}_{0.75}{\mathrm{Ni}}_{2}$. Heat capacity measurements performed in magnetic fields of 1 and 2 T allowed us to estimate the isothermal magnetic entropy and adiabatic temperature changes for ${\mathrm{Dy}}_{1\ensuremath{-}x}{\mathrm{Er}}_{x}{\mathrm{Ni}}_{2}$. Independently, a theoretical analysis was performed for a polycrystalline sample in the frame of a model Hamiltonian taking into account the Zeeman exchange interaction and crystal electric field anisotropy and was expanded to experimental results. Composites with optimum proportions of the individual ${\mathrm{Dy}}_{0.75}{\mathrm{Er}}_{0.25}{\mathrm{Ni}}_{2}$, ${\mathrm{Dy}}_{0.5}{\mathrm{Er}}_{0.5}{\mathrm{Ni}}_{2}$, and ${\mathrm{Dy}}_{0.25}{\mathrm{Er}}_{0.75}{\mathrm{Ni}}_{2}$ components were theoretically determined. The results indicate that the proposed composites are good candidates to be used as the refrigerant material in a magnetic refrigerator performing an Ericsson cycle at low temperatures. The relative cooling power RCP, refrigerant capacity RC, temperature averaged entropy change TEC, and the changes of emitted or absorbed quantity of heat \ensuremath{\Delta}Q were calculated for investigated samples. Direct measurements of the adiabatic temperature change in the vicinity of the magnetic transition temperature were carried out in magnetic fields up to 14 T. The regularities found are discussed in terms of Landau's theory of second-order magnetic phase transitions.

Investigating the structural, magnetic, magnetocaloric and critical behavior of Mg0.35Zn0.65Fe2O4 ferrite

In this study, we successfully prepared the Mg0.35Zn0.65Fe2O4 ferrite sample via standard solid-phase reaction and comprehensive studied its structure, magnetism, magnetocaloric effect and critical behavior. The XRD data refined by Rietveld technology confirms that the sample had a pure phase spinel structure. We conducted a magnetic study on the sample using SQUID and indicated that the sample’ ferromagnetic curie temperature Tc = 295 K, the paramagnetic curie temperature TP = 330 K, and the saturation magnetization can reach 125.41emu/g at an ultra-low temperature of 5 K. We tested the initial magnetization curve near the phase transition temperature (Tc) from ferromagnetic (FM) to paramagnetic states (PM) and produced an Arrott plot that confirmed the presence of a secondary phase transition. The sample’ maximum magnetic entropy change |ΔSMmax| was 1.642 J/kg K and relative cooling power RCP was 185.2 J/kg in the external magnetic field H = 50 kOe. The critical parameter β, γ, δ, and TP were calculated using a Modified Arrott plot (MAP), Kouvel-Fisher (KF) plot and critical isotherm (CI) methods to study the type of magnetic order in the ferromagnetic state that corresponded to the magnetic state equation and mean field model. By analyzing the critical parameters, we obtained the ferromagnetic exchange integral constant J(r) ~ r−4.8498, which was between the 3D Heisenberg model and mean field models and very close to the mean field model, confirming that the long-range and short-range ferromagnetic orderly interactions coexisted with interaction phases and the long-range ferromagnetic orderly interaction dominates.

Influence of Fe-doping amounts on magnetocaloric properties of Gd-based amorphous microfibers

The effects of trace Fe-doping on the magnetic and magnetocaloric performances of Gd-based metallic microfibers were systematically and detailedly investigated in this article. Experimental results indicated that the Gd-based microfibers prepared by the rotated-dipping process are uniform and continuous, with typically amorphous structure characteristics and favorable thermal stability. Curie temperature TC of Gd-based amorphous microfibers increases with the rising of Fe content, and the TC of GdAlCoFe3 microfibers is the highest at 128.7 K (relatively increased by 15.3 K than before doping). Among the general magnetic performance indicators, the saturation magnetization Ms of GdAlCoFe2 microfibers reaches a peak at 264.04 emu/g. Furthermore, the values of magnetocaloric performance indexes of Gd-based amorphous microfibers increase firstly and then decrease with the rising of Fe-doping amount. When the external magnetic field Hex = 50,000 Oe, the maximum magnetic entropy change -ΔSmmax, refrigeration capacity RC and relative cooling power RCP of GdAlCoFe1 microfibers are 10.33 J/kg·K, 748.22 J/kg and 1006.90 J/kg, which increased by 0.07 times, 0.13 times and 0.16 times, respectively than before Fe-doping (namely -ΔSmmax = 9.68 J/kg·K, RC = 663.79 J/kg, RCP = 871.73 J/kg). From the perspective of microstructural changes, Fe-doping results in the formation tendency of atomic clusters and nanocrystals in micro-regions, the orderly orientation of atoms appears, and the magnetic anisotropy increases accordingly. In addition, the 3d electron layer of the doped Fe element in Gd-Al-Co-Fe quaternary alloy system enhances the RKKY indirectly exchange coupling interaction and changes the state of magnetic entropy, which in turn leads to an increase in Curie temperature and an improvement in magnetocaloric performance. Since RC and RCP are the main indicators in engineering applications, the GdAlCoFe1 amorphous microfibers can be selected as a low-temperature magnetic refrigeration working medium to provide technical guarantee for the application of magnetic refrigeration technology.

Structural, magnetic and magnetocaloric properties in RE2Ni1.5Ga2.5 (RE = Dy, Ho, Er and Tm) compounds

The crystal structure together with the magnetic and magnetocaloric properties in RE2Ni1.5Ga2.5 (RE = Dy, Ho, Er and Tm) have been investigated systematically. All the RE2Ni1.5Ga2.5 compounds crystallize in a CaIn2-type structure of (P63/mmc space group). A second-ordered magnetic phase transition (SOPT) from ferromagnetic to paramagnetic (FM to PM) is occurred in RE2Ni1.5Ga2.5 compounds with the Curie temperatures (TC) of approximately 16.1, 10.6, 4.1 and below 2 K for RE of Dy, Ho, Er and Tm, respectively. The magnetocaloric parameters including magnetic isothermal entropy change/temperature-averaged magnetic entropy change -ΔSMmax/TEC (5) and relative cooling power RCP are calculated with the values of 10.01/9.92 J/kg K and 418.6 J/kg for Dy2Ni1.5Ga2.5, 20.12/19.65 J/kg K and 644.1 J/kg for Ho2Ni1.5Ga2.5, 18.07/17.69 J/kg K and 447.1 J/kg for Er2Ni1.5Ga2.5, as well as 18.22/16.75 J/kg K and 330.7 J/kg for Tm2Ni1.5Ga2.5 with magnetic field change (ΔH) of 0–7 T, respectively. Notably, Ho2Ni1.5Ga2.5 exhibits ralatively high magnetocaloric parameters, which suggests that Ho2Ni1.5Ga2.5 is a competitive candidate among the MCE materials in the field of cryogenic magnetic refrigeration (MR).

Magnetic anisotropy and entropy change in trigonal Cr5Te8

We present a comprehensive investigation on anisotropic magnetic and magnetocaloric properties of the quasi-two-dimensional weak itinerant ferromagnet trigonal Cr$_{0.62}$Te single crystals. Magnetic-anisotropy-induced satellite transition $T^*$ is observed at low fields applied parallel to the $ab$ plane below $T_c$. The $T^*$ is featured by an anomalous magnetization downturn, similar to that in structurally related CrI$_3$, and shows a monotonous shift towards lower temperature with increasing field. Magnetocrystalline anisotropy is also reflected in magnetic entropy change $\Delta S_M(T,H)$ and relative cooling power RCP. Given the high $T_c$, Cr$_{0.62}$Te crystals are materials of interest for nanofabrication in basic science and applied technology.

Room temperature magnetocaloric effect in polycrystalline La0.75Bi0.05Sr0.2MnO3

In this work, we have investigated the magnetic and magnetocaloric properties of polycrystalline La0.75Bi0.05Sr0.2MnO3 prepared by sol–gel method. Structural analysis has shown that this compound crystallizes in the rhombohedral structure with R\( \bar{3} \)c space group. The magnetic study revealed that our sample exhibits a ferromagnetic–paramagnetic transition at 300 K. A significant magnetocaloric effect in the vicinity of the room temperature was detected for this sample (for only 2T applied field, the maximum of magnetic entropy change |∆SMax| = 1.75 J/kg K and the relative cooling power RCP = 77.12 J/kg). The obtained results suggest the possibility of using this compound as a magnetic refrigerant.

Rotating magnetocaloric effect in the ferromagnetic Weyl semi-metal Co3Sn2S2

The rotating magnetocaloric effect is of recent interest in the magnetic refrigeration technique, in which the cooling effect is attained by rotating the anisotropic magnetocaloric material from one orientation to the other in a fixed magnetic field. In this work, we report the anisotropic magnetocaloric properties of single crystals of the ferromagnetic Weyl semimetal Co3Sn2S2 for magnetic field H along the c-axis (H∥c) and magnetic field H along the ab-plane (H∥ab). We observed a significant (factor of 2) difference between the magnetocaloric effect measured in both orientations. The rotating magnetocaloric effect has been extracted by taking the difference of the magnetic entropy change (ΔSM) for fields applied in the two crystallographic orientations. Scaling analysis of ΔSM, the rescaled ΔSM(T,H) vs reduced temperature θ curves collapse onto a single universal curve, indicates that the transition from paramagnetic to ferromagnetic phases at 174 K is a second-order magnetic phase transition. Furthermore, using the power law dependence of ΔSM and relative cooling power RCP, the critical exponents β and γ are calculated, which are consistent with the recent critical behavior study on polycrystalline samples of this compound [Yan et al., Solid State Commun. 281, 57 (2018)].

Structural, Magnetocaloric, and Critical Behavior of La0.5Ca0.5Mn1−xVxO3 Manganites Prepared by High-Energy Ball Milling

The high-energy ball milling method has been used to synthesize the polycrystalline powders La0.5Ca0.5Mn1−xVxO3 (x = 0.05, x = 0.10). The Rietveld refinement technique shows that the samples crystallized in the orthorhombic structure with the Pbnm space group. The La0.5Ca0.5Mn0.95V0.05O3 exhibits a second-order phase transition from paramagnetic (PM) to ferromagnetic (FM) state at TC = 208 ± 1 K followed by a second one from FM to charge ordering–antiferromagnetic state at TN = 150.0 ± 0.1 K when decreasing temperature. The substituted sample with 10% amount of vanadium dopant corresponds to the disappearance of the charge-order phase; meanwhile, it was suppressed for 5% of the vanadium in the solid-state route. The Curie temperature TC increases with vanadium content from 208 ± 1 K for x = 0.05 to 255 ± 1 K for x = 0.10. The values of the maximum of the magnetic entropy change under a magnetic field change of 5 T are found to be 2.95 ± 0.04 J kg−1 K−1 and 5.42 ± 0.07 J kg−1 K−1 corresponding to a relative cooling power RCP = 128.4 ± 0.3 and 220.8 ± 0.7 for x = 0.05 and x = 0.10 respectively. The order of phase transition has been determined. The critical exponent study has been performed for La0.5Ca0.5Mn0.9V0.10O3 by using the Arrott plot, Kouvel–Fisher method, and critical isotherm analysis. The measured β, γ, and δ values are in agreement with those expected for the tricritical mean-field model.

Large magnetocaloric effect in van der Waals crystal CrBr3

We study the magnetocaloric effect (MCE) in van der Waals (vdW) crystal CrBr3. Bulk CrBr3 exhibits a second-order paramagnetic-ferromagnetic phase transition with TC = 33 K. The maximum magnetic entropy change −ΔSM near TC is about 7.2 J·kg−1·K−1 with the maximum adiabatic temperature change ΔTadmax = 2.37 K and the relative cooling power RCP = 191.5 J·kg−1 at μ0H = 5 T, all of which are remarkably larger than those in CrI3. These results suggest that the vdW crystal CrBr3 is a promising candidate for the low-dimensional magnetic refrigeration in low temperature region.

Magnetocaloric Effect in La0.67Ba0.33Mn0.95Ni0.05O3 Manganite Near Room Temperature

We report the structural, magnetic, and magnetocaloric properties of La0.67Ba0.33Mn0.95Ni0.05O3 (LBMNO) manganite, synthesized by sol-gel method. X-ray diffraction (XRD) analysis using Rietveld refinement showed that this sample crystallizes in the rhombohedral structure with R $\bar {3}$ c space group. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis were used to confirm the structure formation of the LBMNO material. The temperature dependent magnetization data revealed a transition from ferromagnetic (FM) to paramagnetic (PM) phase at $T_{\mathrm {C}}=$ 308 K. Using Arrott plots, it was found that the transition is of a second order. From the measured magnetization data as a function of magnetic applied field, the magnetic entropy change (−ΔSM) and the relative cooling power RCP have been determined. In the vicinity of $T_{\mathrm {C}}$ (−ΔSM) reached a maximum value of 2.15 J kg− 1 K− 1 and a large RCP value of about 299 J kg− 1 under 5 T− 1. This magnetocaloric effect has been analyzed by considering the Landau theory of magnetic phase transition. Consequently, our sample can be considered a promising material in room-temperature magnetic refrigeration.

Anisotropic magnetocaloric effect in single crystals of CrI3

We report a systematic investigation of dc magnetization and ac susceptibility, as well as anisotropic magnetocaloric effect in bulk CrI$_3$ single crystals. A second-stage magnetic transition was observed just below the Curie temperature $T_c$, indicating a two-step magnetic ordering. The low temperature thermal demagnetization could be well fitted by the spin-wave model rather than the single-particle model, confirming its localized magnetism. The maximum magnetic entropy change $-\Delta S_M^{max} \sim 5.65$ J kg$^{-1}$ K$^{-1}$ and the corresponding adiabatic temperature change $\Delta T_{ad} \sim 2.34$ K are achieved from heat capacity analysis with the magnetic field up to 9 T. Anisotropy of $\Delta S_M(T,H)$ was further investigated by isothermal magnetization, showing that the difference of $-\Delta S_M^{max}$ between the $ab$ plane and the $c$ axis reaches a maximum value $\sim$ 1.56 J kg$^{-1}$ K$^{-1}$ with the field change of 5 T. With the scaling analysis of $\Delta S_M$, the rescaled $\Delta S_M(T,H)$ curves collapse onto a universal curve, indicating a second-order type of the magnetic transition. Furthermore, the $-\Delta S_M^{max}$ follows the power law of $H^n$ with $n = 0.64(1)$, and the relative cooling power RCP depends on $H^m$ with $m = 1.12(1)$.