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Giant Zeeman effect for Mn in wide gap semiconductors: (Ga,Mn)N and (Zn,Mn)O

Wojciech Pacuski 1,2David Ferrand 2Piotr Kossacki 1Joël Cibert 3Jan A. Gaj 1Andrzej Golnik 1Stephan Marcet 2Ekaterina Chikoidze 4Yves Dumont 4Eirini Sarigiannidou 2Henri Mariette 2

1. Warsaw University, Faculty of Physics, Hoża 69, Warszawa 00-681, Poland
2. CNRS-CEA-UJF group Nanophysique et Semiconducteurs, 140 Ave. de la Physique BP87, Grenoble 38402, France
3. Laboratoire Louis Néel, CNRS (LLN), 25 Av. des Martyrs, Grenoble 38042, France
4. CNRS, Laboratoire de Physique des Solides et de Cristallogenese, 1 Place Aristide Briand, Meudon F 92195, France


We present a magneto-optical study of the coupling between Manganese spin and band carriers in wide bandgap diluted magnetic semiconductors (DMS). We use reflectivity, transmission and photoluminescence. We analyze similarities and differences between the giant Zeeman effect in (Ga,Mn)N and in (Zn,Mn)O.
ZnO and GaN are wide bandgap semiconductors with the wurtzite structure, with a weak spin-orbit coupling and a strong electron-hole exchange interaction within the excitons. This combination was an origin of controversies in the determination of basic material parameters. It results also in a complex behavior of the giant Zeeman effect of A and B excitons in the presence of magnetic impurities. It was shown for (Zn,Co)O [1], that not only the transition energies, but also the oscillator strengths are strongly affected by spin-carrier coupling.
We studied (Ga,Mn)N epilayers (grown by MBE), in which most of the Mn ions are in the d4 electronic configuration (Mn3+) with spin S=2 [2]. In the wurtzite structure, spin-orbit coupling in Mn3+ leads to a significant spin anisotropy, with the c-axis as a hard axis. We analyzed the circular polarization causes by the giant Zeeman effect, and we find a ferromagnetic p-d exchange. It is the same sign as in the case of Cr2+ in II-VI DMS's - another example of the d4 electronic configuration.
In ZnO, as in other II-VI's, Mn ions are in Mn2+ state with spin 5/2 and zero orbital momentum. Then the anisotropy is negligible. Thus, the temperature and magnetic-field dependence of the giant Zeeman effect in (Zn,Mn)O follows the usual Brillouin function. Assuming the "normal ordering" for the valence band in (Zn,Mn)O samples grown by MOCVD, the p-d exchange is found to be antiferromagnetic for Mn2+, as for Co2+ [1].
[1] W.Pacuski et al., Phys. Rev. B 73, 035214 (2006)
[2] S.Marcet et al., cond-mat/0604025 (2006)


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Presentation: Oral at E-MRS Fall Meeting 2006, Symposium E, by Wojciech Pacuski
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-15 23:38
Revised:   2009-06-07 00:44