Raman scattering from magnetic excitations in Cd_1-xMn_xTe semiconductor alloys

We have observed antisymmetric Raman scattering from low frequency magnetic excitations in Cd_1-xMn_xTe alloys with 0.1 ≤ × ≤ 0.7. Crystals with x = 0.65 and 0.7 exhibit a magnon line in the antiferromagnetic phase, centered at 10.5 and 12.0 cm^-1 respectively, at 5 K. The frequency and the intensity of these lines decrease markedly with increasing temperature, finally disappearing in the paramagnetic phase. Crystals with 0.4 ≤ × ≤ 0.6 exhibit a similar feature at 5 K over the frequency range 4.5 - 5.5 cm^-1. These are attributed to spin waves originating from antiferromagnetically ordered clusters within their spin-glass phase. All the alloys show a distinct inelastic wing in the paramagnetic phase, which may be related to the magnetic excitations within residual clusters of coupled Mn⁺⁺ spins.