EFFECT OF COBALT SUBSTITUTION ON MAGNETIC-PROPERTIES OF R2FE17 SILICIDES (R=Y, GD, TB, ER, AND TM)

Magnetic characteristics and unit-cell dimensions of the (off-stoichio metric) R2Fe17-type alloys based on R2Fe14-xCoxSi2, where R=Gd, Th, Er , Tm, and Y and x=4 were determined. Partial substitution of Fe by Co slightly increases the saturation magnetization of the alloys and prod uces an average increase in the Curie temperature (T(c)) of 55 K per C o atom. The enhancement of the Curie temperature with the addition of cobalt is attributed to the strengthening of the average 3d-3d exchang e interaction. For Er- and Tm-containing compounds, replacement of Fe by Co has a remarkable effect in shifting the observed spin reorientat ion temperature toward higher temperatures. These results are discusse d in terms of the influence of the interaction of the 4f electrons of the rare-earth ions with the 3d electrons of the transition-metal ions , which modifies the overall anisotropy of the alloys.