High Field Magnetooptics of a Diluted Magnetic Semiconductor Cd_1−xCo_xSe

Reflectance and luminescence spectra of a diluted magnetic semiconductor Cd_1−xCo_xSe (x≈0.01) have been studied in steady high magnetic fields up to 27 T. The bound and free exciton luminescence was clearly observed at 4.2 K. The magnetoreflectance spectra showed that the energy levels of A and B excitons split into two branches in magnetic fields parallel to the c-axis, respectively. The A exciton splitting energy increases proportionally to the magnetization, which results from the sp-d interaction. The linear Zeeman splitting and the diamagnetic shift of the exciton were observed in the magnetic fields higher than 12 T, where the magnetization saturated. We estimated s-d(p-d) exchange constant N₀α = 0.27 eV (N₀β = −2.25 eV), the effective g values |3g_h − g_e| =1.7, and the constant of diamagnetic shift σr=6.8×10⁻⁶ eV/T².