Spin relaxation of Mn ions in (CdMn)Te/(CdMg)Te quantum wells under picosecond optical pumping |
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Authors: | M G Tyazhlov A I Filin A V Larionov V D Kulakovskii D R Yakovlev A Waag G Landwehr |
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Institution: | 1. Institute of Solid State Physics, Russian Academy of Sciences, 142432, Chernogolovka, Moscow Region, Russia 2. A. F. Ioffe Physico-Technical Institute, Russian Academy of Sciences, 194021, St. Petersburg, Russia 3. Physikalisches Institut der Universit?t Würzburg, Würzburg, 97074, Germany
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Abstract: | Spin relaxation of Mn ions in a Cd0.97Mn0.03Te/Cd0.75Mg0.25Te quantum well with photogenerated quasi-two-dimensional electron-hole plasma at liquid helium temperatures in an external
magnetic field has been investigated. Heating of Mn ions by photogenerated carriers due to spin and energy exchange between
the hot electron-hole plasma and Mn ions through direct sd-interaction between electron and Mn spins has been detected. This process has a short characteristic time of about 4 ns,
which leads to appreciable heating of the Mn spin subsystem in about 0.5 ns. Even under uniform excitation of a dense electron-hole
plasma, the Mn heating is spatially nonuniform, and leads to formation of spin domains in the quantum well magnetic subsystem.
The relaxation time of spin domains after pulsed excitation is measured to be about 70 ns. Energy relaxation of excitons in
the random exchange potential due to spin domains results from exciton diffusion in magnetic field B=14 T with a characteristic time of 1 to 4 ns. The relaxation time decreases with decreasing optical pump power, which indicates
smaller dimensions of spin domains. In weak magnetic fields (B=2 T) a slow down in the exciton diffusion to 15 ns has been detected. This slow down is due to exciton binding to neutral
donors (formation of bound excitons) and smaller spin domain amplitudes in low magnetic fields. The optically determined spin-lattice
relaxation time of Mn ions in a magnetic field of 14 T is 270±10 and 16±7 ns for Mn concentrations of 3% and 12%, respectively.
Zh. éksp. Teor. Fiz. 112, 1440–1463 (October 1997) |
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