Density of states of quasi-equilibrium Bose-Einstein condensed magnons in YIG

Abstract

The experimental observation of quasi-equilibrium Bose-Einstein condensation of magnons in yttrium iron garnet at room temperature was first reported by Demokritov et al. in 2006. These authors used their experimental data to obtain a fit for the density of states. In this Thesis we examine the density of states from a theoretical perspective. A theoretical model for magnons in yttirum iron garnet is used. From this model a dispersion relation follows, which is used to obtain the density of states. This is first done by approximating the dispersion around the minimum, allowing for an analytical computation of the density of states. Subsequently an expression for the density of states in the form of an integral over the wave number k is obtained from the model without any further approximations. This integral will have to be evaluated numerically, which is left for future work.