Nature of magnetism in Ca3Co2O6

We find using local spin density approximation + Hubbard U band structure calculations that the novel one-dimensional cobaltate Ca3Co2O6 is not a ferromagnetic half-metal but a Mott insulator. Both the octahedral and the trigonal Co ions are formally trivalent, with the octahedral being in the low-s...

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Bibliographic Details
Published in:Physical review letters 2005-10, Vol.95 (18), p.186401.1-186401.4
Main Authors: HUA WU, HAVERKORT, M. W, HU, Z, KHOMSKII, D. I, TJENG, L. H
Format: Article
Language:English
Subjects:
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Exact sciences and technology
General theory and models of magnetic ordering
Magnetic properties and materials
Physics
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Summary:We find using local spin density approximation + Hubbard U band structure calculations that the novel one-dimensional cobaltate Ca3Co2O6 is not a ferromagnetic half-metal but a Mott insulator. Both the octahedral and the trigonal Co ions are formally trivalent, with the octahedral being in the low-spin and the trigonal in the high-spin state. The inclusion of the spin-orbit coupling leads to the occupation of the minority-spin d2 orbital for the unusually coordinated trigonal Co, producing a giant orbital moment (1.57 microB). It also results in an anomalously large magnetocrystalline anisotropy (of order 70 meV), elucidating why the magnetism is highly Ising-like. The role of the oxygen holes, carrying an induced magnetic moment of 0.13 microB per oxygen, for the exchange interactions is discussed.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.95.186401