Renormalization group analysis of the finite two-dimensional XY model with fourfold anisotropy: Application to the magnetic susceptibility of a ferromagnetic ultrathin film

Abstract

The topological phase transition introduced by Kosterlitz and Thouless has become a central concept in condensed matter physics. With the increasing relevance of topological phases to applications in spintronics, it is important to extend the description of the Kosterlitz-Thouless transition in an infinite, isotropic two-dimensional XY ferromagnet to experimentally realizable systems such as a finite, anisotropic ultrathin film with fourfold in-plane anisotropy. Using a renormalization group analysis, this description is used to calculate the magnetic susceptibility for comparison to experiment.