Neutron Powder Diffraction Study on the Crystal and Magnetic Structures of BiCoO3

• Published in: Chemistry of materials 2006-02, Vol.18 (3), p.798-803
• Main Authors: Belik, Alexei A, Iikubo, Satoshi, Kodama, Katsuaki, Igawa, Naoki, Shamoto, Shin-ichi, Niitaka, Seiji, Azuma, Masaki, Shimakawa, Yuichi, Takano, Mikio, Izumi, Fujio, Takayama-Muromachi, Eiji
• Format: Article
• Language: English
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/cm052334z

The crystal and magnetic structures of polycrystalline BiCoO3 have been determined by the Rietveld method from neutron diffraction data measured at temperatures from 5 to 520 K. BiCoO3 (space group P4mm; Z = 1; a = 3.72937(7) Å and c = 4.72382(15) Å at room temperature; tetragonality c/a = 1.267) is isotypic with BaTiO3 and PbTiO3 in the whole temperature range. BiCoO3 is an insulator with a Néel temperature of 470 K. A possible model for antiferromagnetic order is proposed with a propagation vector of k = (1/2, 1/2, 0). In this model, magnetic moments of Co3+ ions are parallel to the c direction and align antiferromagnetically in the ab plane. The antiferromagnetic ab layers stack ferromagnetically along the c axis, forming a C-type antiferromagnetic structure. Refined magnetic moments at 5 and 300 K are 3.24(2)μB and 2.93(2)μB, respectively. The structure refinements revealed no deviation from stoichiometry in BiCoO3. BiCoO3 decomposed in air above 720 K to give Co3O4 and sillenite-like Bi25CoO39.