A cobaltite with a room temperature electrical and magnetic transition: YBaCo 4O 7

Abstract

The physical properties of an oxygen stoichiometric sample, YBaCo 4O 7, have been studied by T-dependent measurements of the electrical resistivity ( ρ), Seebeck coefficient ( S) and magnetization. Its structural characterization by X-ray diffraction reveals an orthorhombic crystallographic cell at room temperature ( Pbn 2 1 space group, a = 6.298 Å , b = 10.939 Å and c = 10.228 Å ). In that structure made of corner shared CoO 4 tetrahedra, the magnetic array of the cobalt cations form a 1:1 regular stacking of Kagomé and triangular layers. All the physical measurements point towards an hysteretic transition in the range 300–310 K, with a sharp increase of both S and ρ at T S as the temperature decreases. A clear similarity to other L BaCo 4 O 7 compound ( L = lanthanide ) is found, supporting strongly the existence of a structural transition at T S . It is also shown that the ionic radius of the L cation governs T S .