  We present Monte Carlo and Langevin micromagnetic calculations to investigate
thermal switching of single-domain ferromagnetic particles. For the Monte Carlo
study we place particular emphasis on the probability that the magnetization
does not switch by time t. We find that this quantity has different behaviors
in different regimes of applied field, temperature, and system size, and we
explain this in terms of different reversal mechanisms that dominate in the
different regimes. In the micromagnetic study of an array of Ni pillars, we
show that the reversal mode is an outside-in mode starting at the perimeter of
the array of pillars.
