Details

Autor(en) / Beteiligte

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

Titel

Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2

Ist Teil von

• Physical review letters, 2007-10, Vol.99 (15), p.157204-157204

Ort / Verlag

United States

Erscheinungsjahr

2007

Link zum Volltext

Quelle

American Physical Society Journals

Beschreibungen/Notizen

• 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.