Magnetic specific heat of Pb1-xEuxTe

The temperature dependence of the magnetic specific heat was studied experimentally and theoretically in the semimagnetic semiconductor Pb1-xEuxTe for x = 0.027 and x = 0.073, over temperature range from 0.15 K to 15 K, in magnetic fields up to 2 T. In zero magnetic field at about 2 K there was a broad maximum in the magnetic specific heat, which was much higher than that predicted by the model of superexchange interaction between nearest neighbours; the maximum values increased with magnetic field. The experimental data were analysed in the framework of a model which takes into account the spin splitting of the ground state of a single Eu+2 ion in the presence of local lattice distortions in the Pb1-xEuxTe mixed crystal. The model describes well the experimental data, especially for lower x-values, where the contribution from singlets dominates. (author)