Thermally Activated Reversal in Magnetic Nanostructures

The miniaturization of magnetic structures plays an important role for fundamental research as well as for technical applications. New experimental techniques allow for a preparation and investigation of magnetic systems of smaller and smaller spatial extension. This leads to an incremental interest in the understanding of the behavior of small magnetic particles and structures down to the nanometer scale. With decreasing size of magnetic particles thermal activation becomes relevant. The understanding of the role of a finite temperature for the dynamical behavior and magnetic stability of ferromagnetic particles is hence a modern subject in micromagnetism. It is interesting from a fundamental point of view as well as for the application development of magnetic devices. The goal of this review is to give an overview on numerical approaches to thermal activation in magnetic systems as far as they can be described by classical spin systems. Here, the established methods are either a numerical solution of the Landau-Lifshitz-Gilbert equation with Langevin dynamics or Monte Carlo simulations. Special emphasis is put on the relation between these two methods and on the possibility to quantify the steps of a Monte Carlo procedure in terms of realistic time intervals.