Dynamical Corrections to the Transition State Theory for Magnetic Systems

Abstract

As magnetic structures in modern technology become smaller and smaller, thermal fluctuations become an increasing concern in the design and production of various devices such as hard drives. It is therefore important from a practical point of view, as well as from the point of view of fundamental science, to have a good description of the rate of thermally induced magnetic transitions. Only for extremely fast transitions can the time evolution be calculated directly and the stability characterized from simulated trajectories. In practical devices, transitions are rare events, on the time scale of the vibrations of the magnetic moments, making direct simulation too computationally demanding. In this thesis, the use of statistical methods followed by short time dynamical corrections are described. Transition state theory is used to bridge the time scales by providing an estimate of the transition rate, and then short timescale dynamical trajectories started at the transition state are to be utilized to obtain an improved estimate of the transition rate.