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arXiv · 0902.1108

Na ordering imprints a metallic kagome lattice onto the Co planes of Na2/3CoO2

H. Alloul·I. R. Mukhamedshin·T. A. Platova·A. V. Dooglav
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Abstract

We report $^{23}$Na and $^{59}$Co nuclear magnetic (NMR) and quadrupolar resonance (NQR) studies for the $x=2/3$ phase of the lamellar oxide Na$_{x}$CoO$_{2}$, which allowed us to establish reliably the atomic order of the Na layers and their stacking between the CoO$_{2}$ slabs. We evidence that the Na$^{+}$ order stabilizes filled non magnetic Co$^{3+}$ ions on 25% of the cobalt sites arranged in a triangular sublattice. The transferred holes are delocalized on the 75% complementary cobalt sites which unexpectedly display a planar cobalt kagomé structure. These experimental results resolve a puzzling issue by precluding localized moments pictures for the magnetic properties. They establish that the quasi ferromagnetic properties result from a narrow band connecting a frustrated arrangement of atomic orbitals, and open the route to unravel through similar studies the electronic properties of the diverse ordered phases of sodium cobaltates.

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H. Alloul, I. R. Mukhamedshin, T. A. Platova, A. V. Dooglav. 2009-02-06. Na ordering imprints a metallic kagome lattice onto the Co planes of Na2/3CoO2. https://doi.org/10.1209/0295-5075/85/47006

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