Magnetic susceptibility of the rare earth element impurities in the IV–VI semiconductors and Curie–Weiss law

Peculiarities of applying the Curie–Weiss law to the analysis of the magnetic susceptibility of the impurities of the rare earth elements in the IV–VI crystals are examined. It is shown that the traditional approach to the determination of the paramagnetic Curie temperature of ferromagnets and antiferromagnets applied to the impurities of ferromagnetic and antiferromagnetic elements in the doped crystal may lead to fundamental mistakes. The results of this examination are used to analyze the high temperature magnetic susceptibility of Eu and Gd impurities in the PbTe doped crystals grown from the melt using the Bridgman method. It is established that the doping of PbTe with Eu leads to the formation of ferromagnetic inclusions and the same doping with Gd leads to the formation of antiferromagnetic inclusions in the crystal. It is shown that these inclusions are most likely the complexes based on the europium or gadolinium oxides EuO and Gd2O3, respectively.