Valence band hybridizing in europium-alloyed lead selenide

The quasibinary compounds (Pb, Sr)Se and (Pb, Eu)Se are compared with each other and with PbSe regarding the shape of the interband optical absorption edge and the photoluminescence spectra. No differences in the edge are detected without magnetic field, if scaling with composition of the gap and of the effective masses is taken into account. Thus admixing of d states from the paramagnetic Eu2+ ions should not take place in the composition up to 10 at.% EuSe. In (Pb, Eu)Se an additional luminescence line was detected, and was attributed to transitions from the conduction band to the Eu2+ 4f states. In magnetic fields up to 7 T this line does not shift, whereas the interband line shifts with B. This shift cannot be explained by the Zeeman and spin splitting of the band states alone, but additional spin-spin interaction between the localized 4f and extended valence band states is proposed.