High-Magnetic Field X-ray Diffraction Studies on Gd5(Ge2 xFex)Si2 (x ¼ 0:05 and 0.2)

We performed the powder X-ray diffraction measurements in magnetic fields up to 5 T for Gd 5 (Ge 1 . 9 5 Fe 0 . 0 5 )Si 2 and Gd 5 (Ge 1 . 8 Fe 0 . 2 )Si 2 . With bearings from 8 K, the matrix of Gd 5 (Ge 1 . 9 5 Fe 0 . 0 5 )Si 2 clearly shows a structural transition from an orthorhombic to a monoclinic structure at the Curie temperature (T C = 276 K). On the other hand, the matrix of Gd 5 (Ge 1 . 8 Fe 0 . 2 )Si 2 with the orthorhombic structure in the ferromagnetic state shows two-phases co-existence of the orthorhombic and the monoclinic structures above T C = 303 K, indicating that a small amount of the matrix participates in the transformation. For both samples, the monoclinic structure is suppressed but the orthorhombic structure is enhanced just above T C by applying a magnetic field, which closely relates to the magnetization process.