Low-temperature specific heat of the diluted magnetic semiconductor mercury cadmium iron selenide

The specific heat of the diluted magnetic semiconductors Hg1-x-yCdyFexSe has been measured for temperatures below 25K. The excess specific heat (Cm) has been extracted by scaling of nonmagnetic lattice contributions. The resulting Cm of these systems reveals a broad maximum at T¿10 K, whereas for low temperatures a Schottky-type exponential decay of Cm can be observed. These phenomena can be fairly well understood on the basis of a simple crystal-field model and a random distribution of Fe2+. On the other hand, no drastic effect of the energy gap is clearly reflected by our data and therefore we suggest that only Fe2+ states involving the valence bands dominate the antiferromagnetic d-d interactions, analogously to the Mn2+ case.