Raman scattering from spin-flip and magnon excitations in magnetic semiconductors

Inelastic scattering of light in magnetic semiconductors related with s-d (d-f) exchange interactions and spin-orbit coupling is discussed. Calculations of the differential cross section for the case of localised d as well as for the nonlocalised s conduction band are performed. It is shown that a new Raman process, related with excitation of spin-flip in the conduction band and of magnons, should occur in the energy range of 0.05-0.5 eV as a consequence of RKKY interaction. In the case of this process and for typical values of s-d exchange interaction lying between 0.05 and 0.1 eV, the differential cross sections range from 10-9 to 10-11 cm2sr-1 and from 10-7 to 10-9 cm2sr-1 s for ferromagnetic and antiferromagnetic semiconductors, respectively. For the Raman scattering from spin-flip and electronic excitations caused by spin-orbit interaction, selection rules for the polarisations of the incident and scattered photons are derived. The differential cross section for spin-flip Raman scattering in europium chalcogenides is found to be 10-9 cm2sr-1s. The results show that using Raman spectroscopy one can measure the values of the d-f (s-d) exchange integral and spin-orbit interaction parameter. The analysis of the dependence of the energy of the magnon-spin-flip Raman processes on an external magnetic field allows one to determine the sign of the RKKY interaction and to find the g-factor for the conduction electrons. The feasibility of applying spin-flip and magnon-spin-flip Raman processes in magnetic semiconductors in the tuning of electromagnetic radiation in Raman lasers is analysed briefly.