Andrew Boothroyd

Abstract:

We present data on the magnetic and magnetoelastic coupling in the hexagonal multiferroic manganite LuMnO3 from inelastic neutron scattering, magnetization, and thermal-expansion measurements. We measured the magnon dispersion along the main symmetry directions and used this data to determine the principal exchange parameters from a spin-wave model. An analysis of the magnetic anisotropy in terms of the crystal field acting on the Mn is presented. We compare the results for LuMnO3 with data on other hexagonal R MnO3 compounds. © 2010 The American Physical Society.

Abstract:

Polarized neutron inelastic scattering has been used to measure spin excitations in ferromagnetic La0.82Sr0.18CoO3. The magnon spectrum of these spin excitations is well defined at low energies but becomes heavily damped at higher energies and can be modeled using a quadratic dispersion. We determined a spin wave stiffness constant of D=94±3 meV Å2. Assuming a nearest-neighbor Heisenberg model we find reasonable agreement between the exchange determined from D and the bulk Curie temperature. Several possible mechanisms to account for the observed spin-wave damping are discussed. © 2010 The American Physical Society.