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MA: Fachverband Magnetismus

MA 45: Micromagnetism/ Computational Magnetics

MA 45.4: Vortrag

Mittwoch, 16. März 2011, 18:15–18:30, HSZ 403

New methodology for micromagnetic simulations of nanocomposites — •Sergey Erokhin, Dmitry Berkov, and Nataliya Gorn — INNOVENT e.V., Pruessingstr. 27B, D-07745 Jena, Germany

A new micromagnetic methodology for numerical simulations of magnetic nanocomposites is presented. It enables to calculate the magnetization distribution and corresponding small-angle neutron scattering (SANS) cross section of a 3D nanocrystalline system.

In our contribution we consider a nanocomposite of the Nanoperm type, which consists of the iron based crystallites with size of around 10 nm (hard magnetic phase) embedded in an amorphous soft magnetic matrix. The basic constituents of our methodology are as follows: (1) The spatial arrangement of the finite elements is random to avoid artifacts caused by the regular element placement. To generate a corresponding mesh, we employ the modified algorithm suggested earlier for the random close packing of spheres. (2) The magnetodipolar interaction between finite elements is computed in the spherical dipoles approximation. Being exact for spherical particles, this approximation results in some computational errors for the polyhedra used in our method. However, these errors are small, because the shape of our finite elements is close to spherical (due to their spatial distribution). (3) The exchange interaction energy is computed using the standard Heisenberg exchange form. The exchange constant is proportional to the volumes of neighbouring finite elements and depends on the spacing between them as in a standard finite-difference approach.