Electrical resistivity and the magnetocaloric effect in Pr,TbAl2 compounds

Abstract

This work presents a systematic investigation of the magnetic, thermodynamic, and electronic transport properties of ${\mathrm{Pr}}_{\left(1-x\right)}{\mathrm{Tb}}_{x}A{l}_2$ pseudobinary compounds, with $x=0.1$, $0.2$, $0.25$, $0.3$, $0.4$, $0.5$ and $0.75$, focusing on the similarities between the magnetocaloric effect and magnetoresistivity. To better understand their electrical resistivity and its behavior under an applied magnetic field, theoretical calculations of the isothermal entropy changes were carried out. This work extends the mean-field approach previously employed to iteratively and self-consistently calculate the eigenvalues and eigenvectors of the system’s Hamiltonian and to reproduce the experimental magnetic contribution to electrical resistivity data at zero applied magnetic field. In addition to providing new parameters that relate electron scattering to the magnetocaloric effect, a comparative and combined analysis of theoretical and experimental data for $\Delta S\left(T,\Delta H\right)$ and $\Delta \rho \left(T,\Delta H\right)$ emphasizes similarities and differences as a function of temperature. While both $\Delta S\left(T,\Delta H\right)$ and $\Delta \rho \left(T,\Delta H\right)$ display similar shapes around and above the magnetic transition temperature, $T_C$, at lower temperatures, electron scattering and magnetic entropy appear to be differently influenced by the sublattices’ behavior, which depends on the temperature and the concentration $x$. This offers a valuable contribution to the understanding of the phenomena exhibited by these materials. Consequently, from this study, a clear connection between technological applications, such as magnetic refrigeration, and some physical properties of ${\mathrm{Pr}}_{\left(1-x\right)}{\mathrm{Tb}}_{x}A{l}_2$ compounds, could be drawn. Furthermore, their potential for magnetic refrigeration is quantitatively assessed through the calculation of key performance metrics, including the adiabatic temperature change and refrigerant capacity (Relative Cooling Power).