# 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 Komelj^{1} and Manfred Fähnle^{2} — ^{1}Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia — ^{2}Max-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, *Ni*_{3}*Fe* 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 *B*_{2} 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.