A cobaltite with a room temperature electrical and magnetic transition: YBaCo4O7
V. Caignaerta, A. Maignan, a, , V. Pralonga, S. Héberta and D. Pelloquina
aLaboratoire CRISMAT, UMR 6508 CNRS/ENSICaen, 6 bd du Maréchal Juin, F-14050 Caen Cedex 4, France
Received 2 March 2006; accepted 12 May 2006. Available online 11 July 2006.
The physical properties of an oxygen stoichiometric sample, YBaCo4O7, 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 (Pbn21 space group, a=6.298 Å, b=10.939 Å and c=10.228 Å). In that structure made of corner shared CoO4 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 TS as the temperature decreases. A clear similarity to other LBaCo4O7 compound (L=lanthanide) is found, supporting strongly the existence of a structural transition at TS. It is also shown that the ionic radius of the L cation governs TS.