Magnetic Excitations in a Metallic Antiferromagnet FePt₃

Abstract

Spin waves in an antiferromagnetic ordered alloy FePt₃ have been investigated in a wide range of temperature by means of neutron inelastic scattering techniques. From the dispersion relations of the spin waves at 5 K, the exchange interaction parameters between Fe atoms were determined based on the localized spin model, which were found to extend in long range with an oscillatory character. However, a renormalized spin wave theory with these parameters fails to reproduce the observed temperature dependence of the sublattice magnetization as well as the renormalization of the spin wave energy. This fact, together with the relatively large damping of the spin waves, suggests that the simple localized spin model is not sufficient to describe the spin dynamics in the alloy.