Effective mass of conduction electrons in Cd 1 − x Mn x Te

Electron cyclotron resonance in Cd 1 - x Mn x Te (x = 0, 0.064, 0.097, 0.11) has been studied in high magnetic fields up to 150 T at photon energies in the range 44-117 meV, We found that the band-edge effective mass of theconduction electrons increases significantly with the Mn concentration. For comparison with the experimental results the conduction-band Landau levels were calculated by means of the eight-band Pidgeon-Brown model taking into account the s(p)-d exchange interaction. The increase of the band gap due to the Mn ions alone is not sufficient to explain the observed enhancement of the mass. A possible reason for the mass enhancement is an effect of the sp-d hybridization. We also found that the electron mass decreases significantly with decreasing temperature. A large spin splitting of the Landau levels due to the exchange field qualitatively explains the relative temperature dependence of the mass.