X-ray absorption spectroscopy on layered cobaltates NaₓCoO₂

الأصل · EN

Measurements of polarization and temperature dependent soft x-ray absorption have been performed on NaₓCoO₂ single crystals with x=0.4 and x=0.6. They show a deviation of the local trigonal symmetry of the CoO₆ octahedra, which is temperature independent in a temperature range between 25 K and 372 K. This deviation was found to be different for Co³⁺ and Co⁴⁺ sites. With the help of a cluster calculation we are able to interpret the Co L₂₃-edge absorption spectrum and find a doping dependent energy splitting between the t₂g and the eg levels (10Dq) in NaₓCoO₂.