1. FZU 7.11.20061 Mn-doped Ga(As,P) and (Al,Ga)As ferromagnetic semiconductors J.Mašek, J. Kudrnovský, F.Máca, T.Jungwirth, Jairo Sinova, A.H.MacDonald

2. FZU 7.11.20062 Outline Motivation Enhanced Curie temperature in mixed hosts Defects: substitutional vs. interstitial Mn in the Ga(As,P) and (Al,Ga)As Summary

3. FZU 7.11.20063 Motivation Wider bandgap than in GaAs  Mn d- states closer to the valence band edge  Mn acceptor level deeper in VB and more localized  extend of exchange coupling Smaller lattice constant of GaP  enhanced p-d hybridization

4. FZU 7.11.20064 III-V family: Internal reference rule

5. FZU 7.11.20065 Lattice constant: Vegard’s law

6. FZU 7.11.20066 Tight-binding model

7. FZU 7.11.20067 Tight-binding model – cont.

8. FZU 7.11.20068 Tight-binding model – cont.

9. FZU 7.11.20069 T C : LDA+U calculations mean-field calculations for 5% and 10% Mn

10. FZU 7.11.200610 Range of exchange coupling

11. FZU 7.11.200611 Mn interstitials: formation energies Formation energies E s,i (x s,x i ) of Mn Ga and Mn I as functions of partial concentrations x s and x i. Balanced state: E s (x s,x i ) = E i (x s,x i ).

12. FZU 7.11.200612 Ga(As,P): Mn Ga vs Mn I

13. FZU 7.11.200613 (Al,Ga)As: Mn Ga, Mn Al vs. Mn I

14. FZU 7.11.200614 Substitutional vs.interstitial Mn

15. FZU 7.11.200615 Summary Strength of p-d hybridization is more important for T C high than band structure effect The range of exchange coupling in (Ga,Mn)(As,P) unchanged for less than 50% P Suppressed formation of MnI in (Ga,Mn)(As,P) Remarkable increase of T C in (Ga,Mn)(As,P) No improvement expected in (Al,Ga,Mn)As Preferential formation of Mn I in (Al,Ga)As