Spin Wave Studies in Antiferromagnets

Abstract

<p>The thesis investigates three different aspects of spin wave in simple antiferromagnets:</p> <p>Firstly, the spin wave energies are determined in manganese oxide at low temperatures experimentally using inelastic neutron scattering techniques. This has enabled a determination of the magnetic interactions between the spins.</p> <p>Secondly, the effects of zero-point motion have been studied theoretically. The particular emphasis is on the way in which the motion affects the spin wave energy, the magnetization and the total energy of the magnetic system. It is found that earlier theoretical treatments, which were restricted to unusually simple cases, can be generalised to encompass a much wider set of conditions.</p> <p>Finally, a theoretical investigation has been made of the temperature dependence of spin wave energies. Here again, it is found that earlier work restricted to one simple case of an antiferromagnet can be generalised quite extensively. The treatment gives results which predict a different temperature dependence for spin wave of differing wavelengths. Such a dependence is observed experimentally though the theory does not agree quantitatively in all cases.</p>