  The magnetic relaxation of ferromagnetic powders has been studied for many
years, largely due to its importance to recording technologies. However, only
recently have experiments been performed that resolve the magnetic state of
individual sub-micron particles. Motivated by these experimental developments,
we use droplet theory and Monte Carlo simulations to study the time and field
dependence of some quantities that can be observed by magnetic force
microscopy. Particular emphasis is placed on the effects of finite particle
size. The qualitative agreement between experiments on switching and our
simulations in individual single-domain ferromagnets suggests that the
switching mechanism in such particles may involve local nucleation and
subsequent growth of droplets of the stable phase.
