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