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 Co2MnSi.
[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)