Magnetic Transition and Magnetocaloric Effect of Gd(Ga, X) (X = Al, Si) Alloys

Abstract

The crystal structure, magnetic properties, and magnetocaloric performances of Gd(Ga, x) (x = Al, Si) alloys have been systematically investigated. The single phase with a CrB-type orthorhombic structure (space group Cmcm) was observed for x ≤ 0.5 in GdGa1−xAlx and y ≤ 0.2 in GdGa1−ySiy alloys. All phase transitions of GdGa1−xAlx (0 ≤ x ≤ 0.5) alloys are of second-order and their Curie temperatures (TC) increase with the enhancement of the Al substitution amount. GdGa0.8Si0.2 alloy undergoes a first-order magnetic transition from antiferromagnetic (AFM) state to paramagnetic (PM) state. For Δμ0H of 0–7 T, the values of the maximum magnetic entropy change are 6.6 J/kg K, 7.7 J/kg K, 8.4 J/kg K, and 6.8 J/kg K in GdGa, GdGa0.7Al0.3, GdGa0.5Al0.5 , and GdGa0.8Si0.2 alloys, respectively. The magnetic entropy change is enhanced at the critical composition, which is ascribed to the lattice distortion.