•Magnetocaloric effect (MCE) was studied in (Ce0.71Pr0.07Nd0.22)2Fe17-xAlx alloys.•All the samples adopt the Th2Zn17-type rhombohedral crystal structure.•The effective working temperature and RCP was ...greater than 40 K and 60 Jkg−1, respectively.•Low field large adiabatic temperature change of 5.6 K was realized at H = 1 T.•The performance-cost ratio is larger than some potential magnetic refrigerants.
Magnetocaloric effect (MCE) in multicomponent (Ce0.71Pr0.07Nd0.22)2Fe17-xAlx (x = 0.6, 0.8) alloys was studied using the heat capacity and magnetization data. Both the samples crystallize in a rhombohedral Th2Zn17-type structure. The maximum values of magnetic entropy change (-ΔSM) without hysteresis loss are found to be 1.19 Jkg−1K−1 and 1.23 Jkg−1K−1 with relative cooling power (RCP) values of 52.3 Jkg−1 and 66.4 Jkg−1 under an applied field change of 0–1 T for x = 0.6 and 0.8, respectively. Meanwhile, a wide working temperature range (44/54 K) and a large adiabatic temperature change (ΔTad) of 5.6/5.8 K were also achieved for the present compounds.
The current research focuses on analyzing the magnetic and magnetocaloric properties of REH2(RE=Gd,Tb,Dy) in a CaF2-like face-centered cubic system. Through the application of first-principles ...calculations and Monte Carlo simulations, the following physical parameters are determined: Adiabatic temperature change, isothermal entropy change, and relative cooling power (RCP). The magnetic moments of Gadolinium, Terbium, and Dysprosium calculated by the PWSCF method are 6.76μB, 5.74μB, and 4.65μB respectively, aligning well with experimental results. The compounds underwent a second-order phase transition from antiferromagnetic to paramagnetic at TN=21.7K, 17.6K, and 4.3K respectively for GdH2, TbH2, and DyH2. The isothermal entropy change (−ΔSMmax) reached a maximum value of −11.75J/kg.K, −12.47J/kg.K, and −12.87J/kg.K for GdH2, TbH2, and DyH2 under a magnetic field of 5T. We found also that the hydrogenation of rare earth reduces its magnetic performance while but it enhances its thermodynamic and mechanical stability.
Display omitted
•The thermodynamic and mechanical stability of REH2(RE=Gd,Tb,Dy) compounds are investigated.•The REH2 compounds are metals with an antiferromagnetic state.•The magnetocaloric property values of REH2 compounds indicate that they are potential for low-temperature magnetic refrigeration applications.•Comparing the properties of Gd with REH2 compounds reveals the role of hydrogen in these materials.
Achieving appreciable elastocaloric effect under low external field is critical for solid-state cooling technology. Here, a non-isothermal Phase-Field Model (PFM) coupling martensitic transformation ...with mechanics, heat transfer and magnetostrictive behavior is proposed to simulate Magneto-elastoCaloric Effect (M-eCE) that is induced by magnetic field in a multiferroic composite (e.g., Magnetostrictive-Shape Memory Alloys (MEA-SMA) composite). In the PFM, a nonlinear constitutive hyperbolic tangent model is utilized to model the macroscopic magnetostrictive behavior of MEA, and the heat transfer coupled with phase transformation is employed to calculate the adiabatic temperature change (ΔTad) during M-eC cooling cycles. The influences of magnetic field, geometrical dimension, and ambient temperature on ΔTad are comprehensively investigated. Machine Learning (ML) is further conducted on the database from PFM simulations to accelerate the prediction and design of MEA-SMA composite with an improved ΔTad. It is found that a large ΔTad of 10–14 K and a wide working temperature window of 30 K can be achieved under ultra-low magnetic field of 0.15–0.38 T by optimizing the composite’s geometrical dimension. The present work combining PFM and ML for evaluating M-eCE provides a theoretical framework for the optimization of M-eC cooling devices, and is also potentially extended to other multicaloric effects (e.g., electro-elastocaloric effect).
Display omitted
•A non-isothermal phase-field model is proposed for magneto-elastocaloric effect (M-eCE).•Effects of magnetic field, geometric dimension, and ambient temperature on M-eCE are revealed.•A large temperature change of 10–14 K is achieved by a low magnetic field (0.15–0.38 T).•Machine learning is used to accelerate the prediction and optimization of M-eCE.
High-field magnetocaloric effect of the rare-earth Laves-phase compounds, which show the second-order magnetic phase transition at low temperatures, has been studied theoretically and experimentally. ...Both direct and indirect methods are used to characterize the high-field properties of the adiabatic temperature change, ΔTad, and the magnetic entropy change, ΔSmag, for TbNi2 and DyNi2 compounds, which order ferromagnetically below 37 and 22 K, respectively. Experimental data are compared with theoretical results obtained in the frame of the microscopic model which takes into account the Zeeman exchange interaction and the crystal electric field anisotropy. The high-field magnetocaloric properties near the phase transition are also discussed in the framework of the Landau theory for the second-order phase transitions.
Display omitted
•It is found that DyVO4 has a large magnetocaloric effect under 50 KOe magnetic field.•The structural phase transition of the sample was found in the heat capacity curve and analyzed.•The phase ...transition order of the sample was analyzed by various methods.
We prepared DyVO4 polycrystal by solid-state reaction. We tested the magnetization of the samples under field cooling and zero field cooling conditions, and analyzed the magnetic phase transition. It was found that Dy3+ had a paramagnetism to antiferromagnetism phase transition near 3.9 K. The isothermal magnetization curve of the sample was drawn under 0–5 T magnetic field, and the maximum magnetic entropy change (−Smmax) under 5 T magnetic field was calculated to be 25.5 J/kg. Interestingly, we found that with the increase of magnetic field, the maximum magnetic entropy change tends to move towards high temperature, which also leads to the relative refrigeration efficiency (RCP) as high as 522 J/kg. We think this may be related to the structural phase transition in the material, which is confirmed by two abnormal peaks on the heat capacity curve. The anomaly near 3 K comes from the antiferromagnetic phase transition of Dy3+, while the anomaly near 13 K comes from the structural phase transition from tetragonal phase to orthorhombic phase. With the increase of the magnetic field, the −ΔSm near the structural phase transition is larger. We calculated the adiabatic temperature change (ΔTad) of the sample by the heat capacity, and showed two peaks near the magnetic phase transition temperature and the structural phase transition temperature, with ΔTadmax of 9.9 K. We use heat capacity curve, Arrott plot and phenomenological universal curve to judge the order of phase transition. Finally, we think that the two phase transitions of the sample are all first order, but the hysteresis loop results show that the hysteresis is very small, which makes DyVO4 have a potential application prospect in magnetic refrigeration materials.
Rare-earth orthoferrites (RFeO3) promise in spin storage and spin sensing, but the majority of the magnetic phase transition and intriguing properties occur at low temperatures. Searching for ...higher-temperature or even room-temperature spintronics devices has been a critical challenge in the development of spintronics. We doped Mn ions into Fe sites of DyFeO3 in 10%–50 % ratios to coexist antiferromagnetic and ferromagnetic coupling in the ab plane and elevate their spin reorientation transition (SRT) temperatures. The structural, magnetic, and magnetothermal properties of the Mn-doped DyFeO3 single-crystal system are investigated. With increasing doping ratio, the Néel temperature progressively falls, while the SRT temperature (TSR) continuously rises to the room temperature of 307 K with a 40 % doping ratio, making it promising for room-temperature spin storage devices. When the ratio reaches 50 % (half doping), the magnetic configuration of Dy sublattices changes and a significant magnetothermal effect is observed. Because of low-field metamagnetic phase transition, the magnetic entropy change along the c-axis approaches 10.41 J/kg·K for the half doping crystal at 5 K (0 J/kg·K for DyFeO3, 0.93 J/kg·K for orthorhombic DyMnO3). The large adiabatic temperature change contributed by magnon indicates the exceptional refrigeration efficiency in a direct way. Therefore, it is possible to convert DyFeO3 into a room-temperature spin storage device material or a magnetic refrigeration contender at low temperatures.
•Magnetocaloric effect of Ho3Pd2 is studied using Monte Carlo Simulation and ab initio.•We show that the Ho3Pd2 is electronically stable.•It has a ferromagnetic metallic with 84% spin ...polarization.•Total magnetic moment and the exchange couplings deduced from ab initio calculations.•Maximum value of the magnetic entropy was obtained.
The binary intermetallic Ho3Pd2, crystallize in an U3Si2-type tetragonal structure with the tP10, space group P4/mbm (no. 127). On the basis of Monte Carlo Simulations and ab initio calculations, we have studied the magnetism of the Ho3Pd2 compound. We show that the Ho3Pd2 is electronically stable. It has a ferromagnetic (FM) metallic with 84% spin polarization. The exchange energy calculated between the magnetic configurations confirms that the ground state FM is more stable than the antiferromagnetic (AFM) states. The total magnetic moment and the exchange couplings are deduced from ab initio calculations lead, using Monte Carlo simulations, to a quantitative agreement with the experimental transition temperatures. The maximum value of the magnetic entropy change was obtained near the paramagnetic (PM)-FM transition at transition temperature 9.6 k equal to 18.60 J.kg−1.K−1 for magnetic field ΔH = 5 T. These results are more consistent with the experimental results. Our results suggest that this material is a promising candidate for applications in specific technological fields at low temperatures and moderate fields. The relative cooling power and adiabatic temperature change of Ho3Pd2 compound have been calculated for different values of magnetic field. The obtained value for ΔH = 5 T is 230 J/kg. Arrott plots analysis reveals that our materials exhibit a second order magnetic phase transition.
Measurements of the low-temperature heat capacity performed for the polycrystalline Tb1-xDyxNi2 intermetallic compounds with x = 0.25, 0.5 and 0.75 enable us to determine their Debye temperatures and ...estimate the lattice, electron and magnetic contributions to the heat capacity. The measurements in magnetic fields of 1 and 2 T were performed to find the isothermal magnetic entropy and adiabatic temperature changes which characterize the magnetocaloric effect of these compounds. The experimental data obtained are paralleled by theoretical calculations performed in the frame of a microscopic model, which takes into account the exchange interaction and the crystal electric field anisotropy. For the Tb0.75Dy0.25Ni2 compound, direct measurements of the adiabatic temperature change in the temperature range of the magnetic transition were carried out in magnetic fields up to 14 T. The found regularities are discussed in terms of Landau's theory of second-order magnetic phase transitions. In addition, for the parent binary compound, TbNi2, the change of emitted (absorbed) quantity of heat ΔQ was determined using direct measurements.
Display omitted
