Magnetic transition and magnetocaloric effect of Gd₄Sb_3-xR_x (R=Si, Ge, Sn, 0 ≤ x ≤ 0.75) compounds

The magnetic properties and magnetocaloric effect (MCE) of Gd₄Sb_3-xR_x (R = Si, Ge, Sn, x = 0, 0.25, 0.5, 0.75) compounds have been studied systematically. The Curie temperature (T_c) of these compounds can be tuned from 270 K to 305 K depending on the substitution amount. All the compounds undergo a second-order magnetic transition from ferromagnetic (FM) state to paramagnetic (PM) state and exhibit considerable reversible MCE near room temperature. The maximum of magnetic entropy change (ΔSMmax) for a magnetic field change of 7 T can reach 4.25 Jkg^-1K^-1 in Gd₄Sb₃ phase and independent on Si substitution amount. By Ge and Sn substitution, reduced ΔSMmax of 3.5 and 4.25 Jkg^-1K^-1 can be obtained in Gd₄Sb_2.75Ge_0.25 and Gd₄Sb_2.75Sn_0.25 alloys respectively. The considerable MCE with no hysteresis and working temperature near room temperature suggests that these materials could be promising candidates as ambient magnetocaloric materials.