Computational micromagnetics: prediction of time dependent and thermal properties
Thomas Schrefl, W. Scholz, Dieter Suess, J.Fidler
J. Magn. Magn. Mater., 226-230 (2001) 1213-1219
Finite element modeling treats magnetization processes on a length scale of
several nanometers and thus gives a quantitative correlation between the
microstructure and the magnetic properties of ferromagnetic materials.
This work presents a novel element/boundary element micro-magnetics solver
that combines a wavelet-based matrix compression technique for magnetostatic
calculations with a BDF/GMRES method for the time integration of the
Gilbert equation of motion. The simulations show that metastable energy
minima and nonuniform magnetic states within the grains are important
factors in the reversal dynamics at finite temperature. The numerical solution
of the Gilbert equation shows how reversed domains nucleate and expand.
The switching time of submicron magnetic elements depends on the shape of
the elements. Elements with slanted ends decrease the overall reversal time,
as a transverse demagnetizing field suppresses oscillations of the
magnetization. Thermal activated processes can be included adding a
random thermal field to the magnetic field. Thermally assisted reversal
was studied for CoCrPtTa thin-film media.
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Oct. 5, 2001