Jeu. 24/05/2018 10:30 Salle des Séminaires, Bâtiment 21, Etage 4
ZAWADZKI Wlodek (Académie de sciences POLOGNE)
Semimagnetic semiconductors: introduction and properties of ZnMnTe
Introduction to semimagnetic semiconductors (diluted magnetic semiconductors, DMS) is given. Semimagnetic properties of ZnMnTe are described, as obtained by parallel studies of magneto-reflectivity (MR) and magneto-photoluminescence (MPL). Properties of MR resonances are presented and explained. Spin-polarized MPL spectra are shown, exhibiting simultaneous presence of paramagnetic Mn-ions, excitons and donor- acceptor pairs. A coefficient of MPL circular light polarization P(Mn) is introduced and it is demonstrated that it as an important quantity characterizing a semimagnetic material. A relation between the Zeeman shifts of exciton transitions due to exchange interaction with mobile carriers and Mn-ions and P(Mn) due to internal recombination of Mn-ions is revealed. An enhancement of binding energies with increasing magnetic field for excitons localized by potential fluctuations is demonstrated and explained. Simultaneous presence of Mn paramagnetic ions and residual nonmagnetic impurities in ZnMnTe provides for a rich physical picture.
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