Comprehensive inelastic neutron scattering study of the multiferroic .

Abstract

Using high-resolution inelastic neutron scattering, we examine the spin dynamics of in the collinear AF1, the spiral AF2, and the cycloidal AF5 phases. The spin wave excitations are well described by a Heisenberg model with competing long-range exchange interactions ( up to 12th nearest neighbors) and the single-ion anisotropy induced by the spin-orbit interaction. While the exchange constants are relatively unchanged, the dominant effect of doping is to change the single-ion anisotropy from easy axis in the collinear AF1 phase to easy plane in the two multiferroic phases.