The giant magnetocaloric effect between 190 and 300 K in the Gd 5Si xGe 4− x alloys for 1.4⩽ x⩽2.2

Abstract

A detailed investigation of the phase relationships and physical properties (isothermal magnetization, heat capacity and magnetocaloric effect) of heat treated Gd 5Si x Ge 4− x alloys indicate that the monoclinic Gd 5Si 2Ge 2-type phase is stable at 1570 K over the composition range of 1.5⩽ x⩽2.1. All of the alloys exhibit a first order magnetic–crystallographic phase transformation on cooling and/or application of a magnetic field in the paramagnetic state, which is accompanied by the giant magnetocaloric effect. The maximum values of the isothermal magnetic entropy change decrease systematically but non-linearly with the increasing Si concentration ( x), and the giant magnetocaloric effect is observed between 190 ( x=1.5) and 300 K ( x=2.1).