Seminars Archive

Electronic induced phase instabilities in intercalation compounds of titanium dichalcogenides

Abstract
Intercalation compounds based on transition metals dichalcogenides may be considered as natural analogues for artificial multilayered structures. They attract an interest as model materials for study of mutual influence between crystal/electronic structure of a different scale and properties of the materials. For example, intercalation compounds with magnetic metals give a possibility to create a sequence of magnetic layers separated by nonmagnetic interstitials. In contrary with artificial systems there is a possibility to vary the density of occupation of interlayer space with practically constant distance between the layers. We have found that intercalation leads to formation of localized states near Fermi level due to hybridization of valent states of intercalant and surrounding host lattice. Binding energy and a width of these states are determined by character of interaction of intercalant with host lattice and have strong temperature dependence. We have established that impurity states derived by intercalated magnetic metals are spin-polarized. It makes intercalation compounds perspective for spintronics, for study an influence of spin polarization on kinetic, magnetic and thermodynamic properties of the materials. Strong temperature dependence of a character of chemical bond between intercalated object and host lattice obtains a possibility of a decay of homogeneous state with extraction of other phases, which have en epitaxial relation with host lattice. As examples of such precipitations we have got superconducting FeSe impurity phase with tetragonal structure, superparamagnetic and ferromagnetic Fe-clusters. Impurity inclusions have a coherent relation with host TiSe2 or TiTe2 lattice. The methods of synthesis and characterization of crystals developed by us (for both pristine transition metals dichalcogenides and intercalation compounds) give the possibility to perform the measurements using single crystal samples. Architecture of composites is in a close relation with electronic structure of intercalation material, which represents a specific interest.