$^{17}$O NMR Measurements on Superconducting Na$_{0.35}$CoO$_{2} \cdot y$H$_{2}$O

Yoshihiko Ihara; Kenji Ishida; Kazuyoshi Yoshimura; Kazunori Takada; Takayoshi Sasaki; Hiroya Sakurai; Eiji Takayama-Muromachi

doi:10.1143/jpsj.74.2177

arXiv · cond-mat/0506751

$^{17}$O NMR Measurements on Superconducting Na$_{0.35}$CoO$_{2} \cdot y$H$_{2}$O

Yoshihiko Ihara·Kenji Ishida·Kazuyoshi Yoshimura·Kazunori Takada·Takayoshi Sasaki·Hiroya Sakurai·Eiji Takayama-Muromachi

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Abstract

An $^{17}$O NMR measurement was performed on nonoriented polycrystalline Na$_{0.35}$CoO$_2 \cdot y$H$_2$O with superconducting (SC) transition temperature $T_\text{c} = 4.6$ K. A weak temperature dependence was observed in the Knight shift at the O site ($^{17}K$). The spin part of $^{17}K$ ($^{17}K_{\rm spin}$) is estimated from the plot of $^{17}K$ against bulk susceptibility $χ$. The $^{17}K_{\rm spin}$ decreases in the SC state, indicative of the decrease in the in-plane component of the spin susceptibility. The nuclear spin-lattice relaxation rate $1/T_1$ at the O site $^{17}(1/T_1)$ shows a good scaling with $1/T_1$ at the Co site $^{59}(1/T_1)$. This indicates that the spin fluctuations at the O site originate from the Co spin dynamics. The relationships between $^{17}(1/T_1T)$ and $^{17}K_{\rm spin}$ and between $^{17}(1/T_1T)$ and $^{59}(1/T_1T)$ show the development of incommensurate fluctuations at {\bf q $\sim$ 0} other than {\bf q $=$ 0} below 30 K. A clear indication of ferromagnetic correlations at {\bf q $=$ 0} was not observed from the present $^{17}$O-NMR studies.

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Yoshihiko Ihara, Kenji Ishida, Kazuyoshi Yoshimura, Kazunori Takada, Takayoshi Sasaki, Hiroya Sakurai, Eiji Takayama-Muromachi. 2005-06-29. $^{17}$O NMR Measurements on Superconducting Na$_{0.35}$CoO$_{2} \cdot y$H$_{2}$O. https://doi.org/10.1143/jpsj.74.2177

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