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In this work, we report the magnetic and magnetocaloric properties of the Gd 1−y Pr y Ni 2 compounds from both experimental and theoretical points of view. It is worth noting that this series shows a variety of magnetic arrangements depending on the Pr concentration, including paramagnetism, ferrimagnetism and ferromagnetism. Our experimental work consists of the systematic analysis of the magnetic properties of the compounds with y = 0.0, 0.25, 0.5, 0.75 and 1.0, which includes temperature and magnetic field dependence of the magnetization, heat capacity and isothermal entropy change obtained by isothermal magnetization curves. Also, we developed a model Hamiltonian, which takes into account the exchange interactions among Gd-Gd, Gd-Pr and Pr-Pr ions, the Zeeman interaction for both ions and the crystalline electrical field interaction for the Pr ions. We systematically investigated the magnetic properties of the series and obtained a good agreement when compared with our experimental data. [ABSTRACT FROM AUTHOR]

We report the anisotropy of magnetic field-induced entropy change in rare earth Er 1 - y Tb y Al 2 compounds (y = 0.00, 0.25, 0.50, 0.75 and 1.00). In the present work, we use a model Hamiltonian that includes the crystalline electrical field anisotropy in both Er and Tb magnetic sublattices, chemical disorder in exchange interactions among Er-Er, Tb-Tb and Er-Tb magnetic ions and the Zeeman effect. We investigated the isothermal magnetic entropy change Δ S T for a magnetic field of 1 T rotating from a hard 〈0 0 1〉 to the easy 〈1 1 1〉 direction. We also performed a systematic analysis of the reorientation temperature as a function of the magnetic field intensity. The anisotropic magnetocaloric effect highlights the applicability of this effect on the rotating magnetic refrigeration. [ABSTRACT FROM AUTHOR]

We report on the magnetic and magnetocaloric effect calculations in rare earth Er 1− y Tb y Al 2 compounds ( y =0.00, 0.25, 0.5, 0.75 and 1.00). Our model Hamiltonian has contributions of the crystalline electrical field anisotropy in both Er and Tb magnetic sublattices, disorder in exchange interactions among Er–Er, Tb–Tb and Er–Tb magnetic ions and the Zeeman effect. The magnetization, the isothermal entropy change (Δ S T ) and the adiabatic temperature change (Δ T ad ) dependence on temperature were simulated and, compared with the experimental data available. [ABSTRACT FROM AUTHOR]

• Mean field model applied to predict magnetothermal properties of H o 1 - x D y x A l 2 (x = 0, 0.05, 0.10, 0.15, 0.25 and 0.50) • Multiple applied field directions lead to better reproduction of polycrystalline nature of the samples. • Heat capacity and magnetocaloric effect from modeling and experiment agree reasonably well. Magnetic and magnetocaloric properties of H o 1 - x D y x A l 2 compounds with x = 0 , 0.05 , 0.10 , 0.15 , 0.25 and 0.50 , modelled using a Hamiltonian that includes the exchange interactions between Ho-Dy, Ho-Ho and Dy-Dy ions in addition to the crystalline electric field and the Zeeman effects, have been compared with those determined experimentally. In order to reproduce experimentally observed global ferromagnetic ordering temperatures and spin reorientation transition temperatures as x Dy varies, the exchange interactions between Ho-Dy and Ho-Ho were set as free parameters and adjusted to match the experimental results. We demonstrate that heat capacity of polycrystalline materials in non-zero magnetic fields can be satisfactory reproduced by using the average of multiple magnetic field directions with respect to the crystallographic coordinate system, while reasonably good agreement between experimentally determined and theoretically predicted magnetocaloric effects can be achieved considering an average of only three field directions. [ABSTRACT FROM AUTHOR]

Abstract: We report the calculations on the magnetocaloric and barocaloric effects in ferromagnetic series Tb y Gd(1− y )Al2. Our model includes the crystalline electrical field interaction, exchange interactions among Tb–Tb, Gd–Gd and Tb–Gd magnetic ions and the Zeeman effect for an anisotropic system. The lattice and electronic entropies were included in adiabatic processes. The magnetocaloric effect calculated for magnetic field changes along the easy magnetic direction 〈111〉 is in good agreement with the experimental data. Calculation along the hard magnetization direction 〈001〉 predicts anomalous magnetocaloric effect, which was ascribed to the spin reorientation processes. From the available experimental data of Curie temperature dependence on pressure, the exchange model parameters were scaled and the barocaloric effect was calculated. [Copyright &y& Elsevier]

• Mean-field model applied to predict the magnetothermal properties of D y 1 - x T b x A l 2 (x = 0.00, 0.15, 0.25, 0.30, 0.35, 0.40 and 0.75) • Multiple applied field directions lead to better reproduction of polycrystalline nature of the samples. • Heat capacity and magnetocaloric effect from modeling and experiment agree reasonably well. In this work, we developed a theoretical model Hamiltonian, in the mean field approximation, to describe the magnetic and magnetocaloric behavior of the series of compounds D y 1 - x T b x A l 2 (x = 0.00 , 0.15 , 0.25 , 0.30 , 0.35 , 0.40 and 0.75). We adjusted the exchange parameters λ D y D y , λ T b T b , and λ D y T b to obtain the spin reorientation temperatures T S R and the critical temperature T C for each compound in the series. The results obtained by the Hamiltonian model agree satisfactorily with the experimental results. The heat capacity curves with and without an applied magnetic field, adiabatic temperature variation and isothermal entropy variation were modeled and compared with the experimental data. As the experimental results show, our model was also able to reproduce the change in the spin reorientation process: a first order spin reorientation transition appears for concentrations x = 0.15, 0.25, 0.30, 0.35, and no spin reorientation transitions after x = 0.40. [ABSTRACT FROM AUTHOR]

Abstract: One of the biggest challenges in materials science is to understand the microscopic mechanisms responsible in storage and release material entropy. TbN compound, which presents non-degeneracy in ground state, was studied and the calculated magnetocaloric effect is in good agreement with the recent experimental data. Also inverse magnetocaloric effect and spin reorientation transition were predicted in TbN. The theoretical investigations were carried out using a Hamiltonian, which includes the crystalline electrical field, Zeeman and exchange interactions. [Copyright &y& Elsevier]

Abstract: The magnetocaloric effect (MCE) in the DyNi2, DyAl2 and Tb1− n Gd n Al2 (n=0, 0.4, 0.6) was theoretically investigated in this work. The DyNi2 and DyAl2 compounds are described considering a model Hamiltonian which includes the crystalline electrical field anisotropy. The anisotropic MCE was calculated changing the magnetic field direction from 〈111〉 to 〈001〉 in DyNi2 and from 〈100〉 to 〈011〉 in DyAl2. The influence of the second- and first-order spin-reorientation phase transitions on the MCE that occurs in these systems is discussed. For the calculations of the MCE thermodynamic quantities in the Tb1− n Gd n Al2 systems we take into account a two sites magnetic model, and good agreement with the available experimental data was obtained. [Copyright &y& Elsevier]