Raman electron paramagnetic resonance in Zn_1-xCo_xTe and Cd_1-xCo_xTe

Electronic Raman transitions due to the spin flip of the 3d electrons of Co²⁺ in Zn_1-xCo_xTe and Cd_1-xCo_xTe (x<~0.01) are observed at ħω_PM=g(Co²⁺)μ_BH with g(Co²⁺)=2.295±0.010 and 2.310±0.002, respectively. The intensity of Raman electron paramagnetic resonance (Raman-EPR) shows strong resonant enhancement when the incident or scattered photon energy coincides with that of a Zeeman component of the free exciton. Under resonant conditions, the Raman spectra display “ZnTe-like” (or “CdTe-like”) and “CoTe-like” longitudinal optical (LO) phonons in combination with the spin-flip transitions, a consequence of the Fröhlich interaction. In Zn_1-xCo_xTe, even the ZnTe-like TO phonon exhibited EPR sidebands but mediated by the deformation potential; the large p-d spin-spin exchange interaction in Co²⁺-based II-VI diluted magnetic semiconductors is the underlying microscopic mechanism.