Magnetic Field Dependence of Energy Barrier of Perpendicular Nanomagnet

Based on the nudged elastic band model, we investigate the thermal energy barrier and its field dependence of a circular-shaped perpendicular nanomagnet for various exchange constants and cell sizes. We find that the energy barrier depends not only on the cell size but also on the exchange stiffness constant when the switching is governed by the domain-wall nucleation and propagation. We show that analyzing the switching probability curve based on the field-dependent energy barrier equation for the single-domain switching can underestimate the energy barrier so that one has to use the correct field dependence of energy barrier, which can be obtained numerically.