Bi, Pb-3d Transition Metal Perovskite Oxides as Functional Materials

Abstract: 

Structural, electrical and magnetic properties of Bi, Pb-3d transition metal perovskite oxides stabilized by high-pressure synthesis at several GPa are discussed. Stereochemical 6s² lone pairs of Bi³⁺ and Pb²⁺ induce polar distortions as typically observed in PbTiO₃ and BiFeO₃. 6s² (Bi³⁺ and Pb²⁺) and 6s⁰ (Bi⁵⁺ and Pb⁴⁺) charge degree of freedom enables intermetallic charge transfer transition. These are coupled with magnetism or charge state of transition metals resulting in various functionalities. In particular, magnetization reversal by electric field in BiFe_1-xCo_xO₃ , negative thermal expansion in modified BiNiO₃ and PbVO₃ and systematic charge distribution changes in PbMO₃ (M: 3d transition metal) are highlighted.