High-pressure synthesis and magnetic and electrical properties of A- and B-site ordered quadruple perovskites*

Perovskite shows flexible crystal structures as well as various charge and ionic combinations, giving rise to many interesting physical properties. At present, perovskite is one of the most intriguing systems in condensed matter physics. In this talk, we will introduce a few both A-site and B-site ordered quadruple perovskite oxides synthesized by high pressure and high temperature techniques. In particular, we show that PbCoO₃ with a peculiar charge combination of Pb²⁺Pb⁴⁺₃Co²⁺₂Co³⁺₂O₁₂ exhibits spin state, charge state, crystal structure, and metal-insulator transitions under high pressure. Others like CaCu₃Co₂Re₂O₁₂ and LaCu₃Co₂Re₂O₁₂, show exotic magnetic and electrical properties. Specifically, CaCu₃Co₂Re₂O₁₂, a strong insulator, possesses antiferromagnetic ordering at A-site and ferrimagnetic ordering at B-site. If Ca is replaced by La, ferrimagnetic half metallicity is observed in LaCu₃Co₂Re₂O₁₂.