Ferromagnetic to Canted-Ferrimagnetic Transition in Fe(Pd, Pt)3

Magnetization and neutron-diffraction measurements were made on the pseudo-binary Cu3Au-type ordered alloys Fe(PdxPt1−x)3 down to 4.2°K. The magnetic transition reported earlier for compositions near x=0.6 is found to correspond to a rapid but continuous change, as the temperature is lowered below ∼140°K, from pure ferromagnetism (as in FePd3) to a state in which the Fe moments open out into a simple canted structure (with two sublattices arranged identically to those in the pure antiferromagnet FePt3). The Pd, Pt moments are always parallel to the net ferromagnetic Fe moment; these moments vanish for compositions x<0.5. The occurrence and nature of this transition can be readily explained within a molecular field model in which the Pd, Pt moments are induced by and are a rapidly saturating function of the net exchange field from the Fe moments.