Regensburg 1998 – scientific programme

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AM: Magnetismus

AM 7: Dünne magnetische Schichten und Vielfachschichten, magnetooptische Schichten I

AM 7.2: Invited Talk

Tuesday, March 24, 1998, 10:15–10:45, H10

Numerical simulations of remagnetization processes in thin polycrystalline magnetic films with a random anisotropy — •D.V. Berkov¹ and N.L. Gorn² — ¹INNOVENT e.V., Goeschwitzer Str. 22, D-07745 Jena, Germany — ²Institut fuer Physikalische Hochtechnologie, Helmholtzweg 4, D-07743 Jena, Germany

Evaluation of the dipolar interaction field H_dip is the most time-consuming step in micromagnetic algorithms despite the Fast Fourier transformation (FFT) technique recently introduced. The problem is especially serious for systems with periodic boundary conditions because in this case the standard FFT-technique based on the convolution theorem can not be applied. Calculation of H_dip from the corresponding Poisson equation leads to large unphysical oscillations of this field due to the unavoidable sharp cut-off of the Fourier spectrum of the dipole field.
We have developed a new algorithm which enables a fast and exact evaluation of H_dip in dipolar systems with periodic boundary conditions. The algorithm uses the combination of the FFT-technique with the modified Ewald method. Results of numerical simulations of the remagnetization processes in polycrystalline thin magnetic films with the random single-grain anisotropy and the intergrain exchange are presented. The well known ripple-like structures are observed. The dependence of the ripple spectrum on various model parameters is analyzed. Possible applications of our method to numerical simulations of the equilibrium and non-equilibrium thermodynamics of magnetic systems are discussed.