Dynamics of the Kerr rotation from samples A, B, and C measured at the temperature of with the excitation wavelength of . Inset: Kerr rotation of LT-GaAs sample measured under the same conditions.
Kerr rotation as a function of delay time within a short time for samples (a) A and B and (b) samples B and C at the temperature of with the excitation wavelength of . Inset (b): Reflectivity of sample C under the same conditions.
(a) Kerr rotation of sample C as a function of the pump photon energy at with constant laser powers of for the pump and for the probe. The probe pulse is delayed for . (b) Dynamics of the Kerr rotation at two excitation wavelengths of 780 and for sample C at . An arbitrary relative vertical shift is made for clarity.
(a) Temperature dependent pump-induced Kerr signals in the Voigt geometry with a magnetic field of for sample C. (b) Measured factor and precession frequency as a function of temperature. Inset: Temperature dependence of the remanent magnetization along the in-plane  direction. (c) A schematic diagram for the temperature dependence of the internal field . The thick solid and dashed lines represent the ferromagnetic and the paramagnetic phase, respectively. The dark region represents the amount of Mn ions aligned along the direction by the photoexcited holes. The thin solid line represents a temperature dependence of the internal field along the direction when the coupling between the Mn ions and photoexcited holes is considered.
Transient Kerr signal for sample D in the Voigt geometry with a magnetic field of . The coherent precession realized by pump (open square) and coherent amplification and destruction realized by two sequential pump pulses with a temporal separation of , using the two pump pulses with circularly copolarized (open circle) and oppositely polarized helicities (cross), respectively.
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