THEORY OF FARADAY-ROTATION IN SEMIMAGNETIC SEMICONDUCTORS

A microscopic theory of interband Faraday rotation in semimagnetic semiconductors is presented, which takes into account both the wavevector dependence of the exchange interaction and the anisotropy of the mixing of valence band electron wavefunctions when a magnetic field is applied. Comparison of its conclusion and the experimental spectra confirms that the decrease in wavevector of the exchange interaction depends neither on the manganese concentration nor on the sample temperature as already observed for Gamma and L exciton shifts. The small value of the exchange half-width (k(0) = 2.6 x 10(6) cm(-1) for a Lorentzian shaped exchange interaction in CdMnTe) also indicates that the values of the exchange integrals at k = 0 could be somewhat larger than those derived from the magnetic field dependence of excitonic transition frequencies.