Ab-initio studying of spin states of sodium cobaltate Na${}_{2/3}$CoO${}_2$

Abstract

Puzzling properties of sodium cobaltates Na${}_x$CoO${}_2$ become an issue of numerous recent theoretical and experimental investigations because of very high thermopower and intricate phase diagram of this material. Experiments indicated Na${}_{2/3}$CoO${}_2$ to have a kagome-like cobalt sublattice, which implies additional complexity of this strongly correlated system. In the present work we have employed the ab-initio GGA+U modeling method to investigate spin states of Na${}_{2/3}$CoO${}_2$, using an exact crystal cell established in the experiment. Stability of sodium imprint for concentration $x=2/3$ proposed in the publications has been obtained. An AFM-A type magnetic ordering has been recognized as a ground state. Moreover, a competition between low spin state (LS) and intermediate spin state (IS) has been established to depend on on-site Hubbard $U$ correction parameter. LS state has been identified as a ground state of Na${}_{2/3}$CoO${}_2$.

16 pages, 7 figures

References in corpus (16)

• Restoring the density-gradient expansion for exchange in solids and surfaces
• Generalized gradient approximation for solids and their surfaces
• Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy
• Electron correlation and Fermi surface topology of Na${}_x$CoO${}_2$
• Na Induced Correlations in Na${}_x$CoO${}_2$
• The Fermi surface of Na${}_x$CoO${}_2$
• Na ordering imprints a metallic kagome lattice onto the Co planes of Na2/3CoO2
• Na atomic order, Co charge disproportionation and magnetism in Na${}_x$CoO${}_2$ for large Na contents
• Elliptical hole pockets in the Fermi surfaces of unhydrated and hydrated sodium cobalt oxides
• Local moment, itinerancy and deviation from Fermi liquid behavior in Na${}_x$CoO${}_2$ for $0.71\le x\le 0.84$
• Itinerant in-plane magnetic fluctuations and many-body correlations in Na${}_x$CoO${}_2$
• 59Co NMR evidence for charge and orbital order in the kagome like structure of Na2/3CoO2
• The origin of strong correlations and superconductivity in Na${}_x$CoO${}_2$
• Strong correlations enhanced by charge-ordering in highly doped cobaltates
• The electronic structure of the Na${}_x$CoO${}_2$ surface
• Spin fluctuations, magnetic long-range order and Fermi surface gapping in NaxCoO2

Cited by in corpus (1)

• Origin of the electron disproportionation in the metallic sodium cobaltates