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Victor Pavlov

Ioffe Institute of Russian Academy of Sciences, Russia

Title: Photo-induced magneto-optical phenomena in magnetic semiconductors: europium chalcogenides

Biography

Biography: Victor Pavlov

Abstract

Europium chalcogenides EuX (X = O, S, Se, Te) are a compact group of magnetic semiconductors with unique electronic, magnetic, optical and magneto-optical properties. The physical properties of the europium chalcogenides EuX are determined by the electronic structure of the Eu2+ ions, which have strongly localized 4f7 electrons with a large spin S = 7/2. A photo-induced Faraday effect (FE) was studied in the chalcogenides EuTe and EuSe by the optical pump-probe technique using continuous lasers and a broadband light source. The photo-induced FE was investigated as a function of the intensity of light, magnetic field, and temperature. Figure 1 shows field dependences of the photo-induced FE in EuTe at various optical pumping intensities. It has been established that resonant excitation of the 4f75d0 → 4f65d1 optical electric-dipole transition in EuTe produces magnetic polarons with a quantum efficiency of about 10% and a magnetic moment exceeding 600 μB for EuTe and 6000 μB EuSe at low temperatures. A quantum mechanical model has been developed for calculating the photoinduced FE associated with the formation of giant magnetic polarons in EuTe. The developed theory describes well the experimentally observed dependencies. The optical pump-probe technique with a femtosecond time resolution was used to study ultrafast dynamics in EuTe near the absorption band gap. A magnetic-field-induced crossover from the inverse FE to the optical orientation was observed. In conclusion, a number of new photo-induced optical effects in magnetic semiconductors EuX were observed.