Magnetic Properties, Magnetic Field-induced Entropy Change And Phase Transition Research In Fe-based La(Fe, Si)₁₃ Compounds

Room magnetic refrigeration using the magnetocaloric effect (MCE) of solid-state working substances has attracted tremendous attentions during the last few years. NaZn₁₃-type La(Fe,Si)₁₃ compounds with large MCE may be potentially useful for magnetic refrigeration applications. In this paper, we mainly researched magnetic properties, magnetic field-induced entropy change and phase transition in Fe-based La(Fe,Si)₁₃ compounds. This work may be useful for the research of the magnetic refrigeration. Following are the main results:The ingots with the composition of LaFe_13-xSi_x (1.2≤x≤2.2) were prepared by arc-melting, and subsequently homogenized by annealing for a long time. The samples were mainly composed of a NaZn₁₃-type phase. The dependence of magnetization on the magnetic field H was measured at different temperatures for LaFe_13-xSi_x (1.2≤x≤2.2) compounds, and the entropy change (AS) was calculated using Maxwell relation. The variation of AS with H was discussed according to both the Landau second-order phase transition theory and the scalinglaw under mean-field approximation. The results show that the relation of ΔS ∝ H^2/3 is satisfiedfor the LaFe_13-xSi_x compounds. The parameters obtained by the simulation of peak value of entropy change can be used to determine the degree of first-order magnetic phase transition.According to a series of isothermal magnetization curves around Curie temperature T_c ofLaFe_13-xSi_x (1.2～1.7) compounds, we obtained their respective paramagnetic susceptibility x. The temperature dependence of x is well described by the Curie-Weiss Law formally. Thesimulated Curie parameter C has large diversity with the Curie constant C obtained by calculation.We researched the variety of the phase transition temperature T_C with the magnetic field H. According to the results of the thermomagnetic curves of LaFe_13-xSi_x (x=1.3,1.4,1.5) at different magnetic fields, we can obtain the relation of the phase transition temperature T_C and the corresponding magnetic field H. We conclude that this relation can be well simulated by the...