Raman spectroscopy of the paramagnetic spin flip in ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Mn}}_{\mathit{x}}$Te, the role of band-gap excitons as intermediate states, and optically detected electron-nuclear double resonance

We have studied the paramagnetic resonance signal (PRS, Δm=+1) of the 3${\mathit{d}}^5$ spin of ${\mathrm{Mn}}^{2+}$ in ${\mathrm{Cd}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Mn}}_{\mathit{x}}$Te epilayers and, less extensively, in a quantum-well structure by means of Raman spectroscopy in an external magnetic field of 6 T at low temperatures. The exciting laser or the scattered light were in resonance with electronic transitions (free exciton transitions) between the valence and the conduction band. The resonances have been observed by continuously tuning the wavelengths of the exciting dye laser in Voigt and Faraday backscattering geometries. For the off-resonance case the PRS is only expected in Voigt geometry with crossed polarizations of incident and scattered light (single resonance case, either ingoing or outcoming). Contrary to that, in resonance, the transition appears with large intensities as double resonances in the ‘‘forbidden’’ parallel polarizations and also in Faraday configuration. These results can be interpreted by considering a spin flip of a nucleus with I≥1/2 ${(}^{111}$Cd${,}^{113}$Cd${,}^{125}$Te${,}^{55}$Mn) simultaneously with the reorientation of the electronic spin of the 3d shell.