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BiPbFeO with 1:1 mixture of Bi and Pb having charge degrees of freedom at the A-site of perovskite oxide ABO is obtained for the first time by high-pressure synthesis. Comprehensive synchrotron X-ray powder diffraction, optical second harmonic generation, Mössbauer spectroscopy, and hard X-ray photoemission spectroscopy measurements revealed that BiPbFeO is a canted antiferromagnetic insulator crystalizing in a nonpolar tetragonal 4/ structure with √2 × √2 × 2 unit cell and has unusually Pb charge disproportionated BiPbPbFeO charge distribution. The valence of transition metal in BiPbO changes from 3.

Observation of novel charge ordering and spin reorientation in perovskite oxide PbFeO.

PbMO (M = 3d transition metals) family shows systematic variations in charge distribution and intriguing physical properties due to its delicate energy balance between Pb 6s and transition metal 3d orbitals. However, the detailed structure and physical properties of PbFeO remain unclear. Herein, we reveal that PbFeO crystallizes into an unusual 2a × 6a × 2a orthorhombic perovskite super unit cell with space group Cmcm.

Stabilized Charge, Spin, and Orbital Ordering by the 6s Lone Pair in BiPbMnO.

Bi and Pb ions with charge degree of freedom depending on 6 and 6 electronic configurations were combined with the Mn ion in a perovskite oxide. Comprehensive theoretical and experimental investigations revealed the BiPbMnMnO charge ordered state with CE-type spin and d orbital orderings as observed in LaCaMnO, NdSrMnO, and BiSrMnO. The charge and orbital orderings were preserved above 500 K owing to the stereochemical activity of Bi and Pb ions which stabilized the structural distortion.

Hydrothermal Synthesis of Pyrochlore-Type Pentavalent Bismuthates CaBiO and SrBiO.

The pyrochlore-type CaBiO and SrBiO have been synthesized from a low-temperature hydrothermal route using NaBiO·nHO as a starting material. The crystal structures of these compounds were refined using synchrotron powder X-ray diffraction data. The cell parameters were found to be a = 10.