The giant magnetocaloric effect in Gd5Si2Ge 2 with low purity gadolinium

Abstract

The giant magnetocaloric effect Gd5Si2Ge2 alloy was prepared with 99wt% low purity commercial Gd. Powder XRD and magnetic measurements showed that the Gd5Si2Ge2 alloy annealed at 1200°C for 1 h had a significant magnetic- crystallographic first order phase transition at about 270 K. The maximal magnetic entropy change is 17.55 J · kg-1 · K-1 under a magnetic field change of 0-5 T. The distinct increase of magnetic entropy change belongs to the first-order phase transition from the orthorhombic Gd5Si 4-type to the monoclinic Gd5Si2Ge 2-type after high temperature heat-treatment.