Raman scattering study of the magnetic excitations in diluted magnetic semiconductors in the presence of an external magnetic field

We report the observation of Raman scattering associated with the magnetic excitations in diluted magnetic semiconductors, Cd1-xMnx Te in particular, in an applied magnetic field. A sharp Raman line due to the spin flip of the 3d electrons of Mn2, corresponding to the mS=±1 transition, occurs in the paramagnetic phase. Close to band-gap resonance, the mS=±1 transition in combination with the zone-center LO phonons as well as the mS=±2 transition are present. In addition to the internal transitions of Mn2, this resonance suggests a new Raman mechanism involving interband transitions in conjunction with the exchange interaction between band electrons and Mn2. In the magnetically ordered low-temperature phase, the magnon feature splits into two components in the presence of an applied magnetic field. As the temperature is lowered and the crystal becomes magnetically ordered, the Mn2 spin flip of the paramagnetic phase evolves into the higher-energy component of the magnon.