Static and time-resolved magneto-optical spectra of the ferromagnetic semiconductor (Ga,Mn)As show that a pulsed photoexcitation with a fluence of $10\mu \mathrm{J}/{\mathrm{cm}}^2$ is equivalent to the application of an external magnetic field of about 1 mT, which relaxes with a decay time of 30 ps. This relaxation is attributed to the spin relaxation of electrons in the conduction band and is found to be not affected by interactions with Mn ions.

• Received 13 November 2003

DOI:https://doi.org/10.1103/PhysRevLett.92.237203