# Dresden 2006 – wissenschaftliches Programm

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# MA: Magnetismus

## MA 25: Spin-Electronics I

### MA 25.9: Vortrag

### Donnerstag, 30. März 2006, 12:15–12:30, HSZ 103

**Magnetism and spin-polarization of half-metallic ferromagnets at finite temperatures** — •Marjana Ležaić, Phivos Mavropoulos, Jussi Enkovaara, Gustav Bihlmayer, and Stefan Blügel — IFF, Forschungszentrum Jülich, D-52425 Jülich

Half-metallic ferromagnets (HMF) present
a spin-polarization *P* of 100% at
the Fermi level.
At elevated temperatures, however, the spin-polarization is reduced.
We investigate the effect of temperature on
the band gap of HMF which contain more than one magnetic atom in the unit cell,
and describe the mechanisms which lead to the drop of polarization.

We use the full-potential linearized augmented plane-wave
method [1] to calculate the exchange constants of the Heisenberg model and
apply a Monte Carlo method to find the magnetization *M*(*T*) and the Curie temperature.
Additionally, a mean-field like description of the system at *T*>0 is obtained
with the coherent-potential approximation to the disordered local moment state
calculated within the Korringa-Kohn-Rostoker Green function method [2].

For multicomponent HMF we cannot confirm
the proposed model which assumes that *P*(*T*)∼ *M*(*T*) [3].
The presence of different magnetic components can lead to a drop
of *P* at *T*>0 which is much faster than the drop of *M*(*T*).
This effect can be drastic and depends largely on the strength of the hybridization
among the components.
We describe the effects of temperature in more detail for
NiMnSb and Co_{2}MnSi.

[1] `http://www.flapw.de `

[2] H. Akai and P. H. Dederichs, Phys. Rev. B **47**, 8739 (1993)

[3] R. Skomski and P. A. Dowben, Europhys. Lett. **58**, 544 (2002)