MAGNETIC-PROPERTIES OF R(2)CO(17-X)AL(X) COMPOUNDS (R=HO, DY, Y)

The magnetic properties of Ho2Co17-xAlx and Dy2Co17-xAlx compounds (x = 2, 3, 4 and 5) have been investigated by magnetic measurements and X -ray diffraction. The compounds with x = 5 do not stabilise in a 2-17 structure. The Ho2Co17-xAlx compounds with x = 2, 3 and 4 show with in creasing temperature, a spin reorientation from the basal plane to the c-axis. The origin of this reorientation is the change in the Co-subl attice anisotropy from planar to easy-axis upon substitution of Al for Co. This has been confirmed by measurements on Y2Co17-xAlx The spin r eorientation shifts to lower temperatures with increasing Al concentra tion, indicating that the strength of the easy-axis Co-sublattice anis otropy increases. As the Dy-sublattice anisotropy is significantly lar ger than the Ho-sublattice anisotropy, the Dy compounds show no spin r eorientation. The Curie temperatures of both series decreases linearly but strongly with increasing Al concentration.