Electric transport and magnetism in novel layered cobaltates with rare-earths


The project is directed to a new class of intercalation systems Ln(x)CoO2 (Ln=La,Y,rare-earth), prepared by an ionic exchange from the isostructural sodium cobaltate. Their structure is based on hexagonal layers of the edge-sharing CoO6 octahedra that alternate along the c-axis with layers of lanthanide ions. Through the variable content of Ln3+ (x1/3), an electronic behavior of the cobalt subsystem, in particular the conduction and thermopower, is effectively controlled. Our aim is to optimize the technology of the ionic-exchange using the rare-earth nitrates or halides, to vary the mixed valency Co3+/Co4+ by deintercalation or alkali-earth substitution, and to explore systematically the structural, magnetic and electric properties of the products. For a theoretical analysis, the ab-initio and effective Hamiltonian calculations will be undertaken. It is expected that the insertion of magnetic rare-earths will make the electric transport sensitive to external magnetic field.