Na order and Co charge disproportionation in NaCoO
arXiv:1410.1489 · doi:10.1016/j.physb.2014.11.040
Abstract
We have synthesized and characterized different stable phases of sodium cobaltates NaCoO with sodium content . We demonstrate that Na NMR allows to determine the difference in the susceptibility of the phases and reveals the presence of Na order in each phase. Co NMR experiments give clear evidence that Co charge disproportionation is a dominant feature of Na cobaltates. Only a small fraction ( 25%) of cobalts are in a non-magnetic Co charge state whereas electrons delocalize on the other cobalts. The magnetic and charge properties of the different Co sites are highly correlated with each other as their magnetic shift scales linearly with their quadrupolar frequency . This reflects the fact that the hole content on the Co orbitals varies from site to site. The unusual charge differentiation found in this system calls for better theoretical understanding of the incidence of the Na atomic order on the electronic structures of these compounds.
7 pages, 6 figures, accepted to proceedings of ECRYS-2014, will be published in Physica B
References in corpus (10)
- Evidence of a single nonmagnetic Co3+ state in the Na1CoO2 cobaltate
- Electronic texture of the thermoelectric oxide Na0.75CoO2
- Na ordering imprints a metallic kagome lattice onto the Co planes of Na2/3CoO2
- Na atomic order, Co charge disproportionation and magnetism in NaCoO for large Na contents
- Magnetic fluctuations and specific heat in NaxCoO2 near a Lifshitz topological transition
- Evolution of Co charge disproportionation with Na order in NaCoO
- From Hubbard bands to spin-polaron excitations in the doped Mott material NaCoO
- Complex magnetic differentiation of cobalts in NaCoO with 22K Néel temperature
- Sodium Ion Ordering in NaxCoO2
- Instabilities induced by Light in Liquid Crystal Cells with a Photo-Responsive Substrate