Thermoreflectance of CdCr2S4 near the Curie point

The thermoreflectance (TR) spectrum of the ferromagnetic semiconductor CdCr2S4 (Tsub(c) = 86 K) is measured between 24 and 330 K at photon energies ranging from 1.5 to 3.2 eV. A magnetic-order-induced band splitting associated with the earlier observed anomalous C-band (Esub(C) = 1.87 eV at 4.2 K) is found below the Curie-Weiss temperature as well as an additional 'red shifting' structure at higher photon energies. The results support the assumption of a strong coupling between the electron and spin subsystems in ferromagnetic spinels. The mechanism of the spin-dependent electronic processes seems to be more complex than predicted by the simplest models. (author)