Assessing the Thermophysical Properties of Gd, Tb, and GdxTb(1-x) Materials for Magnetic Cooling Application

Abstract

This study investigates the thermophysical properties of gadolinium (Gd), terbium (Tb), and their binary compounds Gd_xTb_(1-x) (x = 0.25, 0.50, 0.75) using mean field theory. The study focuses on calculating magnetocaloric parameters, including magnetic entropy, its variation with magnetic field, specific heat, and the adiabatic temperature change, across magnetic field (B) intensities from 0 to 9 T. The findings indicate that the magnetic entropy has a considerable response to the applied magnetic field, demonstrating a 9.28% reduction in magnetic entropy for Gd at a temperature of 300 K when the field strength escalates from 1.5 to 9 T. Tb has a larger \(\Delta {S}_{\text{m}}\) than Gd under similar conditions. In Gd_xTb_(1-x) compounds, increasing Gd concentration results in a higher Curie temperature, approaching pure Gd, while the peak \(\Delta {T}_{\text{ad}}\) shows a little decline. The peak values of \(\Delta {T}_{\text{ad}}\) are 6 K, 5.86 K, and 5.76 K for x values of 0.25, 0.5, and 0.75 in Gd_xTb_(1-x), respectively, at B 1.5 T. Moreover, Tb demonstrates a significantly higher relative cooling power than Gd, being approximately 34.91% higher at a given B of 1.5 T, whereas Gd and Gd-rich compounds display higher refrigeration capacity in the 250–320 K range. These results provide theoretical insights into the magnetic field–dependent magnetocaloric behavior of Gd, Tb, and Gd_xTb_(1-x) compounds, while highlighting the compositional effects in Gd_xTb_(1-x) compounds.