Effective mass of conduction electrons inCd1−xMnxTe

Electron cyclotron resonance in ${\mathrm{Cd}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$ $(x=0,$ 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 the conduction 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 $s\left(p\right)\mathrm{}-d$ 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 $\mathrm{sp}-d$ 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.