Effect of annealing on the structure and magnetocaloric properties of Gd5Ge2(Sl2−xAlx) compounds

All the samples of Gd₅Ge₂(Si_2-xAl_x(x = 0, 0.1, 0.2, 0.5) were produced by arc melting under argon atmosphere. The crystal structures of all samples crystallized in the orthorhombic structure are studied by X-ray powder diffraction (XRD). The crystal symmetry is preserved while the content of Al changes. By Lakeshore VSM, we have measured M-T curves and M-H curves of the samples at different temperatures. The result shows that the magnetocaloric effect of Gd₂Ge₂(Si_2-xAl_x) is the largest one in all samples at their Curie temperatures, which is 1.4J Kg^-1 · K^-1 where x=0.2. The magnetic-entropy changes are small before and after annealing, which indicated that the uniform magnetocaloric effect phase had been formed before annealing.