  The microwave assisted magnetisation reversal is modelled in a permalloy
micron-sized magnetic ellipsoid. Our simulations confirm that this process
requires less field than magnetisation reversal under a static field. This is
due to a different reversal mode which in case of the microwave-assisted
process is always a ripple structure. During the magnetisation reversal two
stages: nucleation and relaxation are distinguished. The nucleation process is
governed by spinwave instabilities. The relaxation process is related to the
domain expansion through domain wall propagation determined by the precessional
motion of magnetic moments in the center of the domain walls. As a consequence,
the switching time is a complex oscillating function of the microwave
frequency.
