Structural and magnetothermal properties of the Gd5SbxGe4−x system

The crystallographic and magnetic properties of the Gd5SbxGe4−x pseudobinary system were studied by x-ray powder diffraction at room temperature, and the heat capacity, magnetization, and electrical resistivity in the temperature interval 5–320K in applied dc magnetic fields between 0 and 100kOe. The Gd5Sb2.1Ge1.9 compound adopts the Tm5Sb2Si2-type structure (space group Cmca) and orders magnetically via a second order ferromagnetic-paramagnetic transition at 200K, whereas the Gd5SbxGe4−x compounds with x=0.7 and x=1 crystallize in the Sm5Ge4-type structure (space group Pnma) and exhibit first order phase transformations at 45 and 37K, respectively, and therefore, the giant magnetocaloric effect. The heat capacity and electrical resistivity measurements of Gd5Sb0.7Ge3.3 indicate a second order antiferromagnetic transition at 60K in fields 20kOe and lower.