The thermal dependence of the easy magnetisation direction of tetragonal Er1-xYxCo10Mo2 and
ErCo 10-yNiyMo2 compounds were studied from the angular dependence of the magnetisation vector
measured on oriented powders. Whereas one of the studied materials exhibits rather usual first-order
transitions at TSR, the other materials present quite complex and unusual spin reorientation which are
discussed by considering the different contributions to the anisotropy. ?? 2003 Published by Elsevier B.V.
