X-ray absorption spectroscopy on layered cobaltates Na_xCoO_2

Abstract

Measurements of polarization and temperature dependent soft x-ray absorption have been performed on Na_xCoO_2 single crystals with x=0.4 and x=0.6. They show a deviation of the local trigonal symmetry of the CoO_6 octahedra, which is temperature independent in a temperature range between 25 K and 372 K. This deviation was found to be different for Co^{3+} and Co^{4+} sites. With the help of a cluster calculation we are able to interpret the Co L_{23}-edge absorption spectrum and find a doping dependent energy splitting between the t_{2g} and the e_g levels (10Dq) in Na_xCoO_2.

arXiv comment7 pages, 8 figures

References in corpus (22)

• Spin entropy as the likely source of enhanced thermopower in $\rm\bf Na_xCo_2O_4
• Charge-ordering, commensurability and metallicity in the phase diagram of layered Na(x)CoO(2)
• Evidence for a Low-Spin to Intermediate-Spin State Transition in LaCoO3
• An Electronic Model for $Co{O}_2$ layer based systems: Chiral RVB metal and Superconductivity
• A different look at the spin state of Co${}^{3+}$ ions in CoO${}_5$ pyramidal coordination
• Unconventional magnetic transition and transport behavior in Na0.75CoO2
• Quantum Critical Behavior and Possible Triplet Superconductivity in Electron Doped CoO2 Sheets
• Giant electron-electron scattering in the Fermi-liquid state of Na_0.7CoO_2
• Crystal Structure of the Sodium Cobaltate Deuterate Superconductor NaxCoO2o4xD2O (x=1/3)
• Bulk antiferromagnetism in $\mathbf{N}{\mathbf{a}}_{0.82}\mathbf{Co}{\mathbf{O}}_2$ single crystals
• Ferromagnetic in-plane spin fluctuations in NaxCoO2 observed by neutron inelastic scattering
• Theory of Sodium Ordering in NaxCoO2
• The crystal growth and characterization of NaxCoO2 and NaxCoO2yH2O
• Charge ordering and magneto-polarons in Na${}_{0.82}$CoO${}_2$
• Orbital Symmetry and Electron Correlation in Na_{x}CoO_2
• Structural transition in NaxCoO2 with x near 0.75 due to Na rearrangement
• Raman Phonons and Ageing-Related Surface Disorder in NaxCoO2
• Bulk Electronic structure of Na${}_{0.35}$CoO${}_2$.1.3H${}_2$O
• Effect of Hydrostatic Pressure on the Superconductivity in NaxCoO2.yH2O
• Polarization dependence of x-ray absorption spectra in Na_xCoO_2
• Spin states and phase separation in La_{1-x}Sr_{x}CoO_3 (x=0.15, 0.25, 0.35) films: optical, magneto-optical and magneto-transport studies
• Stripe correlations in Na${}_{0.75}$CoO${}_2$

Cited by in corpus (8)

• Magnetism and structure of LixCoO2 and comparison to NaxCoO2
• Spin correlations and cobalt charge states: A new phase diagram of sodium cobaltates
• Polarization dependence of x-ray absorption spectra in Na_xCoO_2
• Effective Hamiltonian for transition-metal compounds. Application to Na_xCoO_2
• Electronic structure and Fermi surface tolopogy of Na${}_x$CoO${}_2$
• The origin of a${}_{1g}$ and e${}_g$' orderings in Na${}_x$CoO${}_2$
• Evidence for Oxygen Holes due to d-p Rehybridization in Thermoelectric Sr_{1-x}Rh_{2}O_{4}
• Quasiparticle dispersion near the Fermi surface in Na${}_x$CoO${}_2$