Magnetic Excitations in Transition-metal Oxides Studied by Inelastic Neutron Scattering


Inelastic neutron scattering using a triple axis spectrometer is a very efficient tool to analyze magneticexcitations. We will discuss several recent experiments on transition-metal oxides where orbital degrees of fIeedom playan important role. Different kinds of experimental techniques including longitudinal and spherical polarization analysiswere used in order to determine not only magnon frequencies but also polarization vectors. In layered ruthenates bandsof different orbital character contribute to the magnetic excitations which are of both, ferromagnetic andantiferromagnetic, character. The orbital dependent magnetic excitations seem to play different roles in thesuperconducting pairing as well as in the metamagnetism . In manganates the analysis of the magnon dispersion in thecharge and orbital ordered phase yields direct insight into the microscopic coupling of orbital and magnetic degrees offreedom and helps understanding, how the switching between metallic and insulating phases in manganates may occur.In multiferroic TbMn03 the combination of our polarized neutron scattering results with the infrared measurementsidentifies a soft collective excitation of hybridized magnon-phonon character.Keywords: Inelastic neutron scattering, magnetic excitations. M. BradenInstitute of Physics, University of Cologne, Germany