Orbital degeneracy removed by charge order in triangular antiferromagnet AgNiO2

Abstract

We report a high-resolution neutron diffraction study on the orbitally-degenerate spin-1/2 hexagonal antiferromagnet AgNiO2. A structural transition to a tripled unit cell with expanded and contracted NiO6 octahedra indicates root(3) x root(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 Jahn-Teller distortions. A novel magnetic ground state is observed at base temperatures with the electron-rich S = 1 Ni sites arranged in alternating ferromagnetic rows on a triangular lattice, surrounded by a honeycomb network of non-magnetic and metallic Ni ions. We also report first-principles band-structure calculations that explain microscopically the origin of these phenomena.

4 pages including 4 eps figures, improved Fig 4, to appear in Physical Review Letters

References in corpus (2)

• Spin-1/2 Triangular Lattice with Orbital Degeneracy in a Metallic Oxide Ag2NiO2
• Formation of an unconventional Ag valence state in Ag2NiO2

Cited by in corpus (33)

• Unconventional aspects of electronic transport in delafossite oxides
• Quantum Oscillations of the Metallic Triangular-lattice Antiferromagnet PdCrO2
• Na ordering imprints a metallic kagome lattice onto the Co planes of Na2/3CoO2
• Formal Valence, $d$ Occupation, and Charge-Order Transitions
• Charge disproportionation and collinear magnetic order in the frustrated triangular antiferromagnet AgNiO2
• Frustration-induced nanometre-scale inhomogeneity in a triangular antiferromagnet
• Magnetic Properties of New Triangular Lattice Magnets A${}_4$B'B${}_2$O${}_{12}$
• Competition between supersolid phases and magnetisation plateaux in the frustrated easy-axis antiferromagnet on a triangular lattice
• Spin dynamics of frustrated easy-axis triangular antiferromagnet 2H-AgNiO2 explored by inelastic neutron scattering
• From basic properties to the Mott design of correlated delafossites
• Emergent Heavy Fermion Behavior at the Wigner-Mott Transition
• A fundamental correlative spectroscopic study on LixNiO2 and NaNiO2
• Cascade of field-induced magnetic transitions in a frustrated antiferromagnetic metal
• Direct observation of charge order in triangular metallic AgNiO2 by single-crystal resonant X-ray scattering
• Effect of magnesium doping on the orbital and magnetic order in LiNiO2
• Supersolid phases in a realistic three-dimensional spin model
• Coupled spin-charge order in frustrated itinerant triangular magnets
• Perspectives of the disproportionation driven superconductivity in strongly correlated 3d compounds
• Charge States of Ions, and Mechanisms of Charge-Ordering Transitions
• Variational Monte Carlo Study of a Spinless Fermion t-V Model on a Triangular Lattice: Formation of a Pinball Liquid
• Anomalous temperature evolution of the internal magnetic field distribution in the charge-ordered triangular antiferromagnet AgNiO2
• Magnetic ordering and spin dynamics in $S=5/2$ staggered triangular lattice antiferromagnet Ba${}_2$MnTeO${}_6$
• Noncollinear and noncoplanar magnetic order in the extended Hubbard model on anisotropic triangular lattice
• Pinball liquid phase from Hund's coupling in frustrated transition metal oxides
• Multiorbital kinetic effects on charge ordering of frustrated electrons on the triangular lattice
• Emergent lattices with geometrical frustration in doped extended Hubbard models
• LaBaNiO4: A Fermi glass
• Metal-insulator transition in half-filling two-orbital Hubbard model on triangular lattice
• Charge and orbital order in frustrated Pb3Mn7O15
• Mean-field Study of Charge, Spin, and Orbital Orderings in Triangular-lattice Compounds ANiO2 (A=Na, Li, Ag)
• Two dimensional frustrated magnets in high magnetic field
• Topological Insulators from Electronic Superstructures
• Revisiting the metal-to-metal transition in $2H$-AgNiO${}_2$