Regensburg 2004 – wissenschaftliches Programm

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MA: Magnetismus

MA 11: Magnetische Materialien

MA 11.3: Vortrag

Dienstag, 9. März 2004, 10:45–11:00, H22

The effect of the spin-orbit coupling on the half-metallic band gap — •Phivos Mavropoulos¹, Kazunori Sato¹, Rudi Zeller¹, Peter Dederichs¹, Voicu Popescu², and Hubert Ebert² — ¹IFFForschungszentrum Jülich, D-52425 Jülich — ²Department Chemie/Physikalische Chemie, University of Munich,Butenandtstr. 5-13, D-81377 Munich

We present ab-initio calculations on the effect of spin-orbit coupling to the band gap of half-metals. Due to spin-orbit coupling the majority-spin states are partly flipped and a 100% spin polarisation P cannot exist. As typical systems, we choose the Heusler alloy NiMnSb, the zinc-blende alloys CrAs, CrSb, and MnBi, and the diluted magnetic semiconductors (Ga,Mn)As and (Ga,Mn)N. We find that the majority-spin states are partly reflected into the minority band gap. The DOS for minority electrons in this energy region depends mainly on the strength of the spin-orbit coupling, heavier sp elements resulting in a higher ratio of minority/majority spin DOS. We see a trend of decreasing P at E_F as we go from CrAs (99.6%) to CrSb (98.6%) and finally to MnBi (77%). In NiMnSb we find P=99%. Also, majority states close to the gap edges are easier spin-flipped. This results in P=92% at E_F for (Ga,Mn)As.