Observation of current-induced polarization in (Ga,Mn)As via magneto-optic Kerr measurement

Current-induced Kerr rotation spectra and reflectivity spectra of (Ga,Mn)As and p-GaAs were measured in the absence of the magnetic field via magneto-optic Kerr effect around the energy gap. The dependence of the Kerr rotation and the reflectivity on the laser wavelength show Lorentzian profile. The Kerr rotation depends linearly on the current and the reflectivity depends linearly on the square of the current. The Kerr rotation of P-GaAs is much weaker than that of the (Ga,Mn)As which indicate that the doping of Mn enhance the current-induced spin polarization . The dependence of the Kerr rotation and the reflectivity on the temperature was also measured, both showing red shift of their Lorentzian peaks, a familiar behavior as the absorption edge of GaAs. In addition, we observed the dependence of the Kerr signal on the polarizational direction of the incident beam.