Magnetic, magnetothermal, and magnetoelastic properties of Gd5(Si1.95Ge2.05) near the magnetostructural phase transition

The Gd 5 (Si x Ge 4-x ) system with 0 ≤ x ≤ 2.1 undergoes a magnetostructural phase transition, which can be triggered by a magnetic field above Curie temperature. During the transition, colossal magnetostrictive, giant magnetocaloric, and giant magnetoresistance effects are observed. Experimental studies of the Gd 5 (Si 1.95 Ge 2.05 ) composition using magnetic susceptibility, magnetization, magnetostriction, linear thermal expansion, heat capacity, and direct magnetocaloric effect measurements confirm that both the structural and magnetic phase changes occur simultaneously at 262 K in a zero magnetic field. The magnetocaloric effect values in a low magnetic field (14 kOe) calculated from the heat capacity and measured directly are in reasonable agreement in the high temperature region (above 262 K). Below Curie temperature, the direct measurements show a negative magnetocaloric effect, which is unexpected for a ferromagnetic system and likely originates from a complex metastable process of magnetization, leading to an increase in the entropy of the sample in a low magnetic field.