Crystal structure and magnetic properties of Nd1−xYxCo6.86Hf0.14 compounds

The Nd1−xYxCo6.86Hf0.14 compounds with x=0-0.4 have been investigated by means of X-ray powder diffraction and magnetic measurements. The as-cast Nd1−xYx(Co,Hf)7 compounds crystallize in the hexagonal TbCu7-type structure with the space group P6/mmm. The lattice parameter a and the cell volume V decrease linearly with the Y content while c holds almost constant. The saturation moment per formula unit decreases linearly with the Y content, but the saturation moment per Co atom increases with the Y content. The Curie temperature and the magnetic anisotropy field of the compounds increase with the Y content. The increase of the Curie temperature is mainly related to the increase of the Co-Co exchange interaction due to the volume reduction effect. The Nd1−xYx(Co,Hf)7 compounds with x=0-0.4 show basal plane anisotropy at 5 K. The room temperature easy magnetization direction of the Nd1−xYx(Co,Hf)7 compounds changes from basal plane to c-axis with increase in the Y content. The spin reorientation (SR) transition has been found in the Nd1−xYx(Co,Hf)7 compounds and the SR temperature decreases with the Y content.