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 magnetic
excitations. We will discuss several recent experiments on transition-metal oxides where orbital degrees of fIeedom play
an important role. Different kinds of experimental techniques including longitudinal and spherical polarization analysis
were used in order to determine not only magnon frequencies but also polarization vectors. In layered ruthenates bands
of different orbital character contribute to the magnetic excitations which are of both, ferromagnetic and
antiferromagnetic, character. The orbital dependent magnetic excitations seem to play different roles in the
superconducting pairing as well as in the metamagnetism . In manganates the analysis of the magnon dispersion in the
charge and orbital ordered phase yields direct insight into the microscopic coupling of orbital and magnetic degrees of
freedom 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 measurements
identifies a soft collective excitation of hybridized magnon-phonon character.
Keywords: Inelastic neutron scattering, magnetic excitations. M. Braden;Institute of Physics, University of Cologne, Germany