Monte Carlo simulations were used for a detailed description of magnetic, martensitic and magnetocaloric properties of Ni_2+x Mn_1−x Ga (0.18 ⩽ x ⩽ 0.24) and Ni₅₀Mn₃₄In₁₆ Heusler alloys, which undergo a first-order magnetostructural phase transition. In the simulations we made use of magnetic exchange parameters which were obtained by ab initio calculations. Results of magnetic and lattice contributions to the total specific heat as well as the change in the isothermal magnetic entropy ΔS _mag and the adiabatic temperature ΔT _ad changes around the magnetic and magnetostructural transitions in an external magnetic field agree fairly well with available experimental data.

The magnetocaloric effect (MCE) in an Fe₄₈Rh₅₂ alloy and Sm_0.6Sr_0.4MnO₃ manganite was studied in cyclic magnetic fields. The adiabatic temperature change in the Fe₄₈Rh₅₂ alloy for a magnetic field change (ΔB) of 8 T and a frequency (f) of 0.13 Hz reaches the highest value of (ΔT_ad) of −20.2 K at 298 K. The magnitude of the MCE in Sm_0.6Sr_0.4MnO₃ reaches ΔT_ad = 6.1 K at the same magnetic field change at 143 K. The temperature regions, where a strong MCE is exhibited in an alternating magnetic field, are bounded in both compounds. In the case of the Fe₄₈Rh₅₂ alloy, the temperature range for this phenomenon is bounded above by the ferromagnetic to antiferromagnetic transition temperature in the zero field condition during cooling. In the case of the Sm_0.6Sr_0.4MnO₃ manganite, the temperature range for the MCE is bounded below by the ferromagnetic-paramagnetic transition temperature in zero field during heating. The presence of these phase boundaries is a consequence of the existence of areas of irreversible magnetic-field-induced phase transitions. It is found that the effect of long-term action of thousands of cycles of magnetization/demagnetization degrades the magnetocaloric properties of the Fe₄₈Rh₅₂ alloy. This can be explained by the gradual decrease in the size of the ferromagnetic domains and increasing role of the domain walls due to giant magnetostriction at the ferromagnetic to antiferromagnetic transition temperature. The initial magnetocaloric properties can be restored by heating of the material above their Curie temperature.

In this report, we present results of the direct measurements of the adiabatic temperature change in MnAs_1−xP_x compounds (x = 0, 0.02, 0.025, and 0.03) in cyclic magnetic fields up to 8 T. The substitution of As by P results in a slight shift of the Curie temperature and more notable change in the magnetocaloric effect (MCE) value. Estimations of the lattice and magnetic contributions show that in the MnAs compound, the lattice contribution dominates (about 70% of the total MCE). Substitution of As with phosphorus leads to a decrease in the total value of the MCE, which is caused by a decrease in the lattice contribution, and the magnetic contribution almost does not change in the absolute value. A reversible degradation of the magnetocaloric effect in cyclic magnetic fields is found, which restricts the application of this material to the magnetic cooling technology.

The magnetization, the electrical resistivity, the specific heat, the thermal conductivity, and the thermal diffusion of a polycrystalline Heusler alloy Ni45.37Mn40.91In13.72sample are studied....

Results of the experimental investigations of magnetocaloric effect (MCE) and magnetostriction in Pr_0.7Sr_0.2Ca_0.1MnO₃ manganite in the temperature range of 80–310 K and in magnetic fields up to 80 kOe are presented. The behavior of the MCE is characteristic of materials with magnetostructural phase transitions of the first order. Frequency (1–14 Hz) dependences of the MCE in a magnetic field of 6.2 kOe are investigated. It is shown that near T_C, the ΔT dependence of the frequency f is well described by the expression: $\mathrm{\Delta }\mathrm{T}(f)=\mathrm{\Delta }{\mathrm{T}}_{f=0}-\mathrm{B}{f}^{\mathrm{n}}$ (n = 1.53, B = 0.01185 K/Hzⁿ). The results of the investigation of magnetostriction show that near T_C, the value of magnetostriction is Δɛ = 4.49 ⋅ 10⁻⁴ in a magnetic field of 80 kOe. According to the results of the study of magnetostriction in various magnetic fields, it is shown that the change in the magnetic entropy is directly proportional to magnetostriction ΔS_M = γ₁Δɛ (γ₁ = 2 ⋅ 10⁴ J/kg K). This ratio can serve as another indirect method for estimating the MCE, which shows good agreement with the data of direct caloric measurements.