[Congress Report]Perovskites

The main theme of the session was oxide materials with unusual electronic or magnetic properties. P. Bordet (CNRS, Grenoble) described structural anomalies at the superconducting transition in HgBa2CuO4+d from single crystal powder diffraction and EXAFS spectra. A general treatment of tilting in perovskites and a new computer program to derive the tilt systems was given by P. Woodward (Ohio State, USA). M. Fernandez-Diaz (ILL, Grenoble) reported a remarkable charge disproportionation coupled to a structural transition in the undoped lanthanide nickelate perovskites LnNiO3. The session ended with two talks on layered manganite perovskites. J. Mitchell (Argonne, USA) showed how new CMR Ruddleston-Popper phases could be prepared by controlling oxygen stoichiometry, and V. Caignaert (Caen) described the preparation of La/Ba ordered and disordered polymorphs of La0.5Ba0.5MnO3 and discussed their different physical properties. The session illustrated the continuing challenge to understand the relationships between composition, structure and properties in perovskite oxides.

J.P. Attfield and Juan Rodriguez-Carvajal