Micromagnetic simulation of magnetization reversal in rotational magnetic fields

Transient magnetization states during switching are investigated numerically in thin Co nano-elements of square (100 X 100nm(2)), rectangular (100 x 300nm(2)) and circular (100nm diameter) shapes with a thickness of 20nm. Switching dynamics are calculated for external fields applied instantaneously and for rotational fields with field strengths in the order of the static critical field (H = 0.20-0.32J(s)/mu (0)). Reversal in the unidirectional field proceeds by the nucleation and propagation of end domains toward the center of the particle. It is found that the switching time strongly depends on the Gilbert damping parameter alpha. Small values of alpha ( less than or equal to0.1) lead to shorter switching times of 0.1-0.3 ns. Reversal in rotational fields involves inhomogeneous rotation of the end domains toward the rotational field direction. Depending on the damping parameter, fast switching times ( less than or equal to0.1 ns) are obtained by increasing the field strength to H = 0.5J(s)/mu (0). (C) 2001 Elsevier Science B.V. All rights reserved.