Orbital Degeneracy Removed by Charge Order in Triangular Antiferromagnet AgNiO{sub 2}
- H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom)
- Code 6393, Naval Research Laboratory, Washington, D.C. 20375 (United States)
- Max-Planck Institut fuer Festkoerperforschung, Heisenbergstrasse 1, D-70569 Stuttgart (Germany)
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX (United Kingdom)
We report a high-resolution neutron diffraction study on the orbitally degenerate spin-1/2 hexagonal metallic antiferromagnet AgNiO{sub 2}. A structural transition to a tripled unit cell with expanded and contracted NiO{sub 6} octahedra indicates {radical}(3)x{radical}(3) charge order on the Ni triangular lattice. This suggests charge order as a possible mechanism of lifting the orbital degeneracy in the presence of charge fluctuations, as an alternative to the more usual Jahn-Teller distortions. A novel magnetic ground state is observed at low temperatures with the electron-rich S=1 Ni sites arranged in alternating ferromagnetic rows on a triangular lattice, surrounded by a honeycomb network of nonmagnetic and metallic Ni ions. We also report first-principles band-structure calculations that explain microscopically the origin of these phenomena.
- OSTI ID:
- 21024272
- Journal Information:
- Physical Review Letters, Vol. 99, Issue 15; Other Information: DOI: 10.1103/PhysRevLett.99.157204; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0031-9007
- Country of Publication:
- United States
- Language:
- English
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