Influence of Tb substitution on low-field magnetocaloric effect in Gd₅Si_1.72Ge_2.28 alloy

Abstract

The lattice parameters, magnetic phase transition, Curie temperature and magnetocaloric properties for (Gd_1−xTb_x)₅Si_1.72-Ge_2.28 alloys with x = 0, 0.15, 0.20 and 0.25 were investigated by X-ray powder diffractometry and magnetization measurements. The results show that suitable partial substitution of Tb in Gd₅Si_1.72Ge_2.28 compound remains the first-order magnetic-crystallographic transition and enhances the magnetic entropy change, although Tb substitution decreases the Curie temperature (T_C) of the compounds. The magnetic entropy change of (Gd_1−xTb_x)₅Si_1.72Ge_2.28 alloys retains a large value in the low magnetic field of 1.0 T. The maximum magnetic entropy change for (Gd_0.80Tb_0.20)₅Si_1.72Ge_2.28 alloy in the magnetic field from 0 to 1.0 T reaches 8.7 J/(kg·K), which is nearly 4 times as large as that of (Gd_0.3Dy_0.7)₅Si₄ compound (|ΔS_max| = 2.24 J/(kg·K), T_C = 198 K).

Keywords

rare earth alloy / magnetic entropy change / magnetic phase transition / magnetocaloric effect (MCE)