On the Structural and Electronic Factors Governing the Magnetic Properties of the Hexagonal Perovskite-Type Oxides AxBO3 (A=Ca, Sr, Ba; B=Co, Ni)
✍ Scribed by M.-H. Whangbo; H.-J. Koo; K.-S. Lee; O. Gourdon; M. Evain; S. Jobic; R. Brec
- Publisher
- Elsevier Science
- Year
- 2001
- Tongue
- English
- Weight
- 332 KB
- Volume
- 160
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The hexagonal perovskite-type oxides A x BO 3 (A ؍ Ca, Sr, Ba; B ؍ Co, Ni) consist of (BO 3 ) chains made up of face-sharing BO 6 octahedra and BO 6 trigonal prisms. On the basis of molecular orbital calculations for their structural building blocks we examined why the transition metal atoms in the trigonal prisms of Sr 9/7 NiO 3 and Sr 14/11 CoO 3 occupy the positions away from their trigonal prism centers and why Ba 6/5 NiO 3 and Ca 3/2 CoO 3 exhibit apparently puzzling magnetic properties. Our analysis indicates that the structural building units of the (BO 3 ) chains in these oxides adopt high-spin states to reduce the metal+metal -antibonding interactions between adjacent metal atoms as well as the on-site repulsion. This 5nding led us to predict the number of unpaired spins that the oxides Sr 9/7 NiO 3 , Sr 6/5 CoO 3 , and Sr 14/11 CoO 3 are expected to have.