Polarization-modulated magnetoreflection in magnetic semiconductors: CdCr₂S₄ and EuSe

The polarization-modulated (PM) magnetoreflection technique has been used to study magnetic ordering effects in CdCr₂S₄ and EuSe. The energy gap for direct band-band transitions in CdCr₂S₄ has been measured to be E_G = 2.3 eV, and the exchange splitting of the valence band to be about 0.03 eV. Good agreement with thin film absorption measurements is obtained in the temperature dependence of spectral structure, observed at energies less than E_G, associated with crystal field and charge transfer transitions. No strongly blue-shifting peak is observed with magnetic order. PM magnetoreflection spectra of the E₁ peak of EuSe show a direct manifestation of the spin alignment from the ferrimagnetic to ferromagnetic state of this crystal at 2 K in external fields up to 16 kOe. An attempt is made to explain resonant Raman scattering in EuSe (observed by other workers) in terms of the field-induced shift of one of the polarized E₁ reflectivity components into coincidence with the 5145 Å argon-ion laser line. © 1973.