Effect of Y substitution on the structural and magnetic properties of Dy1-xYxCo5 compounds
Structural and magnetization studies were carried out on Dy1-xYxCo5 [x = 0, 0.2, 0.4, 0.6, 0.8, 1] compounds which crystallize in the hexagonal CaCu5-type structure. Lattice parameters and unit-cell volume increase with Y concentration. Large thermomagnetic irreversibility between the field-cooled and the zero-field cooled magnetization data has been observed in all the compounds, which has been attributed to the domain wall pinning effect. Temperature dependence of magnetization data shows that except DyCo5 and YCo5, all the compounds show spin reorientation transitions in the range of 5-300 K. The spin reorientation temperature decreases from 266 K for x=0.2 to 100 K for x=0.8. Powder x-ray diffractograms of the magnetically aligned samples show that DyCo5 has planar anisotropy at room temperature whereas all the other compounds possess axial anisotropy. The spin reorientation transition has been attributed to a change in the easy magnetization direction from the ab-plane to the c-axis, as the temperature is increased. The anisotropy field and the first order anisotropy constant are found to be quite high in all the compounds except DyCo5. The magnetic properties have been explained by taking into account the variations in contributions arising from the rare earth and transition metal sublattices.