Klimov A. Impurity centres in layer gallium selenide doped by gadolinium.

The dissertation is devoted to detailed study of impurity centres in a layer crystal GaSe:Gd by ESR and ENDOR techniques. Spectra of 8 new paramagnetic centres are registered and interpreted. Parameters of a spin–Hamiltonian describing the observed ESR and ENDOR spectra are determined, and models of the centres are suggested. It is revealed that Gd3+ ions substitute gallium covalent bound pairs in the crystal lattice. For a number of centres the Li+ and Na+ ions compensating charge were found in the intra-layer space. Obtained variety of the centres is caused by lattice sites inequivalence in the layer crystal, distinction in charge compensator natures, formation of complex exchange centres. Information about the structure of defect caused by charge carrier (hole) localization in the vicinity of impurity ion was obtained. ENDOR in a zero magnetic field is found and studied. Its features, advantages and general regularities are investigated. Temperature dependencies of ESR spectra in GaSe:Gd crystal are explained by presence of low-frequency optical oscillations in a phonon spectrum of the layer crystal. It was found for Gd3+ (Na+) centre that the layer structure locally behaves as a regular 3D crystal.