Energy band structure of magnetic semiconductor CdCr₂Se₄ in atomic sphere approximation

Conclusion

In this paper we have made the first calculation of the electron structure of the magnetic spinel semiconductor CdCr₂Se₄ by means of the atomic sphere approximation method [1].

The energy spectrum obtained for valence bands and 3d states of chromium is not inconsistent with experimental results. As regards the red shifting band, our calculation shows (even if we today, at the present stage of energy band calculations for CdCr₂Se₄ and their diverse results [23, 26], consider such an assignment premature) the possibility of the interpretation as the transition from the top of the valence band into the 3d e _g states of chromium, given by us some years ago [10, 12] and used recently by Kambara et al. [23]. The crucial point of such an assignment remains the mechanism leading to the red shift of the transition. The application of the molecular field approximation [23, 8] to such a narrow band is wrong. The temperature behavior of the band edge is more complicated [40]. Also the inclusion of hybridization with a broad conduction band [41] does not give, in more precise treatment [24], hopeful results for the large red shift. Another possible mechanism is changing the structure parameteru of the spinel during cooling [39, 42].