Thermal decay of interacting grains in perpendicular thin-film media

Thermal decay of interacting magnetic grains in perpendicular thin films is studied by a new approach where damping and thermal fluctuations are added to each independent normal mode of the system around equilibrium. Optimal path and asymptotic analysis are used to obtain the collective reversal barrier and the mean exit time. The results show a reduction of thermal decay with decreasing magnetostatic interaction and/or increasing exchange coupling. The reversal barrier of an individual grain using a mean field interaction is compared with allowing neighbors to collectively rotate. It is found that collective effects yield a reversal barrier lower than a mean field analysis. This difference increases with increasing inter-granular interaction.