Spin-Dynamics in the Carrier-Doped $S=1/2$ Triangular-Lattice of Na${}_x$CoO${}_2$-yH${}_2$O

Abstract

We probed the local electronic properties of the mixed-valent Co(+4-x) triangular-lattice in Na{x}CoO{2}-yH{2}O by 59-Co NMR. We observed two distinct types of Co sites for x>=1/2, but the valence seems averaged out for x~1/3. Local spin fluctuations exhibit qualitatively the same trend down to ~100 K regardless of the carrier-concentration x, and hence the nature of the electronic ground state. A canonical Fermi-liquid behavior emerges below ~100 K only for x~1/3.

arXiv comment4 figures. Submitted to PRL on May 13, 2004

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