Regensburg 2002 – wissenschaftliches Programm
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MA: Magnetismus
MA 22: Magnetische Anisotropie
MA 22.1: Vortrag
Freitag, 15. März 2002, 12:00–12:15, H22
Ab-initio electron theory of magnetoelastic phenomena in thin epitaxial films: Achievements and possible limitations — •Matej Komelj1 and Manfred Fähnle2 — 1Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia — 2Max-Planck-Institute für Metallforschung, Heisenbergstraße 1, D-70569 Stuttgart, Germany
Within the framework of the phenomenological theory of magnetoelasticity the magnetic anisotropies and magnetostrictive stresses are calculated for epitaxial magnetic films in various geometries, yielding relation between these quantities and the linear and nonlinear magnetoelastic coefficients. Furthermore, it is shown by the phenomenological theory that these coefficients may be obtained from the change in the total energies of appropriately strained bulk materials when rotating the direction of the magnetization. Finally, the total energy changes are calculated by the ab-initio density functional electron theory. Altogether, we determine the linear and the dominating nonlinear magnetoelastic coefficients for bcc Fe, fcc Co and Ni, Ni3Fe and FeCo, and the implications for the interpretation of the magnetic properties of thin epitaxial films are discussed. For Fe the density functional theory yields a sign of the first-order coefficient B2 which is opposite to the experimentally obtained sign. This may indicate a failure of the density functional theory or a problem with the experiments which so far considered Si-doped Fe instead of pure Fe for the investigation of magnetoelastic coefficients.