  A time-resolved optical pump-probe technique has been applied for studying
the ultrafast dynamics in the magnetic semiconductor EuTe near the absorption
band gap. We show that application of external magnetic field up to 6 T results
in crossover from the inverse Faraday effect taking place on the femtosecond
time scale to the optical orientation phenomenon with an evolution in the
picosecond time domain. We propose a model which includes both these processes
possessing different spectral and temporal properties. The circularly polarized
optical pumping induces the optical electronic transition $4f^75d^0 \rightarrow
4f^65d^1$ forming the absorption band gap in EuTe. The observed crossover is
related to a strong magnetic-field shift of the band gap in EuTe at low
temperatures. It was found that manipulation of spin states on intrinsic defect
levels takes place on a time scale of 19 ps in the applied magnetic field of 6
T.

Materials Science