GD-155 MOSSBAUER-EFFECT AND MAGNETIC-PROPERTIES OF ALUMINUM-SUBSTITUTED AND GALLIUM-SUBSTITUTED GDCU5 AND GDNI5

We have investigated the effect of aluminium and gallium substitution on the Gd-155 Mossbauer spectra of GdCu5 and GdNi5. No marked changes were observed in the values of the electric field gradient derived from the quadrupole splitting of the spectra. This was ascribed to the absence of a strongly preferred substitution of aluminium and gallium into one of the two available non-rare earth sites in GdNi5 and GdCu5. Additional evidence for this was obtained from X-ray diffraction. Further analysis of our data has shown that the earlier reported phase transition in GdCu5 at low temperatures is probably non-existent.