Magnetic susceptibility and specific heat of the semi-magnetic semiconductors Cd1-xFexSe and Hg1-xFexSe and their mixtures

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Abstract
The authors present results concerning the magnetic susceptibility of the recently synthesised diluted magnetic (semi-magnetic) semiconductors Hg1-xFexSe, Cd1-xFexSe and Hg1-x-yCdyFexSe. The high-temperature data (temperature T>or=77 K) obey the Curie-Weiss law. The orbital moment is almost quenched in the system Hg1-xFexSe. The compounds Cd1-xFexSe for xor=0.10 the susceptibility has a maximum for all the systems studied which is interpreted as the onset of the spin glass phase. The temperature dependence of the specific heat for Hg1-xFexSe shows a broad maximum which is also present in the samples without the corresponding maximum in the susceptibility; thus it cannot be associated solely with the spin glass transition. The dominant exchange integral determined from the Curie-Weiss temperature is of antiferromagnetic character for all the systems studied and diminishes with the increasing band gap. The results are discussed qualitatively in terms of the virtual bound state of the 3d electrons in Hg1-xFexSe which transforms gradually into a localised state with growing content of Cd in Hg1-x-yCdyFexSe. The authors also discuss the relative roles of the super-exchange and the Bloembergen-Rowland interactions in these systems.