Abstract
The NdFe10−xCoxMO2 alloy system (x=0,1,3,5,7,10) has been synthesized and studied by x-ray and magnetometry techniques. All of the compounds in this series crystallize in the tetragonal ThMn12-type structure. X-ray-diffraction analyses on aligned powders indicate that the anisotropy in this system is strongly modified by Co substitution. A distinctive feature we observe is that, with increasing Co content, the easy direction of magnetization at 300 K appears to deviate from the c axis for x≤3, and becomes axial for x≥5. The spin reorientations are observed for x=0,1,3. For x≥5, the room-temperature anisotropy field increases with the increase of Co content, i.e., from 18 kOe at x=5 to 34 kOe at x=10, and no spin reorientations are observed. The first-order magnetization process is observed for x≥5. The Curie temperature is considerably enhanced by Co substitution in this system.