Micromagnetic simulation of switching events
T. Schrefl , H. Forster, D. Suess, W. Scholz, V. D. Tsiantos and J. Fidler
in Bernhard Kramer (Ed.), Advances in Solid State Physics, Springer Verlag, 2001, p. 623-635
Magnetic switching of small particles, thin film elements and
magnetic nanowires becomes increasingly important in magnetic
storage and magneto electronic devices. Micromagnetic switching
events are studied using a hybrid finite element / boundary
element method. The space discretization of the Gilbert equation
leads to a system of ordinary differential equations. Its
numerical integration provides the time evolution of the
magnetization under the influence of an external field. Thermal
fluctuations may be treated by a random field. The reversal mode
drastically depends on the Gilbert damping constant. Decreasing
the damping constant from alpha=1 to alpha<=0.1 changes the
reversal mode from uniform rotation to inhomogeneous switching.
The decrease of the damping leads to the formation of vortices in
circular nanodots and to a nucleation process in columnar grains.
Elongated Co particles reverse by rotation if the length of the
particle is smaller than 25 nm. Irreversible switching of longer
particles occurs due to the formation of a nucleus of reversed
magnetization and successive domain wall motion.
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Oct. 18, 2001