Optical orientation of nuclei in nitrogen alloys GaAsN at room temperature |
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Authors: | V K Kalevich M M Afanasiev A Yu Shiryaev A Yu Egorov |
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Institution: | 1. Ioffe Physical Technical Institute, Russian Academy of Sciences, St. Petersburg, 194021, Russia 2. Spin Optics Laboratory, St. Petersburg State University, St. Petersburg, 198504, Russia
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Abstract: | The intensity and giant circular polarization of edge luminescence in a longitudinal magnetic field have been measured in nitrogen alloys GaAsN under circularly polarized pumping. It has been found that these dependences are shifted with respect to zero field by a value B eff. The magnitude of the internal field B eff increases with the pumping intensity and reaches saturation (≈250 G) at large excitation densities. The saturation of the B eff field with growth of pumping indicates that this is a field of nuclei, polarized dynamically due to hyperfine interaction with optically oriented deep paramagnetic centers, rather than a field of exchange interaction created on the center by spin-polarized photo-excited conduction electrons. The short time of nuclear polarization by electrons (<15 μs), measured under modulation of circular polarization of the exciting light with high frequency, points to a small number of nuclei undergoing hyperfine interaction with an electron localized at a center. |
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