Abstract
In the two-dimensional anisotropic classical Heisenberg model with XY symmetry there are nonplanar vortices which exhibit a localized structure of the z components of the spins around the vortex center. We study how thermal noise induces a transition of this structure from one polarization to the opposite one. We describe the vortex core by a discrete Hamiltonian and consider a stationary solution of the Fokker-Planck equation. We find a bimodal distribution function and calculate the transition rate using Langer’s instanton theory (1969). The result is compared with Langevin dynamics simulations for the full many-spin model.
- Received 31 August 1998
DOI:https://doi.org/10.1103/PhysRevB.59.7010
©1999 American Physical Society