Structure and magnetic properties of Gd2Co17−xSix compounds

Abstract The Gd 2 Co 17− x Si x compounds have the rhombohedral Th 2 Zn 17 structure and form for 0⩽x⩽3 . The compounds with 0⩽x⩽0.3 have an easy magnetisation direction parallel to the c axis only at high temperatures. The spin reorientation temperature, leading to a state with easy magnetisation direction perpendicular to the c axis, decreases strongly with increasing Si concentration. The spin reorientation in Gd 2 Co 17 takes place at 940 K, which is substantially lower than that reported previously for Ho 2 Co 17 . The componds with 1⩽x⩽3 have an easy magnetisation direction parallel to the c axis at all temperatures. The Co moments and the Curie temperatures decrease strongly with increasing Si concentration. We also determined the values of the anisotropy constant K 1 which change from negative to positive around x=0.7. This behaviour is discussed in terms of preferential Si substitution.