Magnetism in ordered and amorphous YCo3 and YFe3

Local magnetic moments on cobalt atoms in ordered and amorphous YCo3 differ dramatically, whereas those on iron atoms in ordered and amorphous YFe3 do not. Our energy-band calculations for these systems show that YCo3 in the Cu3Au model structure has an equilibrium lattice constant which lies within a few percent of a volume-induced magnetic instability, whereas the equilibrium lattice constant for YFe3 lies in a region of stable magnetism. The calculations suggest that the difference in the magnetic moment of ordered and amorphous YCo3 is a consequence of this magnetic instability and a difference in the atomic densities of the two forms of this material. This density difference is sufficient to lower the moment for ordered YCo3 but not for ordered YFe3. © 1983 The American Physical Society.