Crystal structure and magnetic properties of Nd1−xYxCo6.8Zr0.2 compounds

The Nd1−xYxCo6.8Zr0.2 compounds with x = 0-1.0 have been investigated by means of X-ray powder diffraction and magnetic measurements. The as-cast Nd1−xYxCo6.8Zr0.2 compounds crystallize in the hexagonal TbCu7-type structure with the space group P6/mmm. The lattice parameters a, c and the cell volume V decrease linearly with the Y content. The saturation moment per formula unit decreases almost linearly with the Y content. However, the saturation moment of per Co atom increases with the Y content, reaches a maximum value at about x = 0.5, then decreases with increasing content of Y. 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−xYxCo6.8Zr0.2 compounds with x = 0-0.8 show basal plane anisotropy at 5 K, but show basal plane (x = 0) or c-axis (x = 0.2-0.8) anisotropy at room temperature. The Nd1−xYxCo6.8Zr0.2 compound with x = 1.0 shows c-axis magnetic anisotropy at both 5 K and room temperature. A spin reorientation transition has been found in the Nd1−xYxCo6.8Zr0.2 compounds and the SR temperature decreases with the Y content.