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Wawrzyńska E, Coldea R, Wheeler EM, et al. Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2. Phys Rev Lett. 2007;99(15):157204doi: 10.1103/PhysRevLett.99.157204.
Wawrzyńska, E., Coldea, R., Wheeler, E. M., Mazin, I. I., Johannes, M. D., Sörgel, T., Jansen, M., Ibberson, R. M., & Radaelli, P. G. (2007). Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2. Physical review letters, 99(15), 157204. https://doi.org/10.1103/PhysRevLett.99.157204
Wawrzyńska, E, et al. "Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2." Physical review letters vol. 99,15 (2007): 157204. doi: https://doi.org/10.1103/PhysRevLett.99.157204
Wawrzyńska E, Coldea R, Wheeler EM, Mazin II, Johannes MD, Sörgel T, Jansen M, Ibberson RM, Radaelli PG. Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2. Phys Rev Lett. 2007 Oct 12;99(15):157204. doi: 10.1103/PhysRevLett.99.157204. Epub 2007 Oct 11. PMID: 17995209.
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Phys Rev Lett. 2007 Oct 12;99(15):157204. doi: 10.1103/PhysRevLett.99.157204. Epub 2007 Oct 11.

Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2.

Physical review letters

E Wawrzyńska, R Coldea, E M Wheeler, I I Mazin, M D Johannes, T Sörgel, M Jansen, R M Ibberson, P G Radaelli

Affiliations

  1. H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, United Kingdom.

PMID: 17995209 DOI: 10.1103/PhysRevLett.99.157204

Abstract

We report a high-resolution neutron diffraction study on the orbitally degenerate spin-1/2 hexagonal metallic antiferromagnet AgNiO2. A structural transition to a tripled unit cell with expanded and contracted NiO6 octahedra indicates sqrt[3]xsqrt[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.

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