Unconventional Upper- and Lower-Critical Fields and Normal-State Magnetic Susceptibility of the Novel Superconducting Compound $Na_{0.35} Co O_2 \cdot 1.3 H_2O$

Hiroya Sakurai; Kazunori Takada; Shunsuke Yoshii; Takayoshi Sasaki; Koichi Kindo; Eiji Takayama-Muromachi

doi:10.1103/PhysRevB.68.132507

paper

Unconventional Upper- and Lower-Critical Fields and Normal-State Magnetic Susceptibility of the Novel Superconducting Compound $N a_{0.35} C o O_{2} \cdot 1.3 H_{2} O$

arXiv:cond-mat/0304503 · doi:10.1103/PhysRevB.68.132507

Abstract

Magnetic properties of the novel layered superconductor, Na $_{0.35}$ CoO $_{2}$ $\cdot$ 1.3H $_{2}$ O have been investigated. From the temperature dependence and field dependence of the magnetization, the superconducting transition temperature, as well as upper- and lower-critical fields have been estimated to be $T_{C} = 4.6$ K, $H_{C 2} (0) = 61.0$ T and $H_{C 1} (0) = 28.1$ Oe. These values give quite unusual phenomenological parameters, \textit{i.e.}, coherent length, penetration depth and Ginzburg-Landau parameter of $ξ = 2.32$ nm, $λ = 5.68 \times 1 0^{3}$ Å and $κ \equiv λ / ξ = 244$ , suggesting an unconventional nature of superconductivity. Normal-state magnetic susceptibility shows an upturn below 130 K, which is confirmed to be inherent by high-field magnetization data. The upturn may have relevance to the mechanism of the superconductivity.

4 pages, 4figures. Submitted to Phys. Rev. Lett

Unconventional Upper- and Lower-Critical Fields and Normal-State Magnetic Susceptibility of the Novel Superconducting Compound Na0.35​CoO2​⋅1.3H2​O

Abstract

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Unconventional Upper- and Lower-Critical Fields and Normal-State Magnetic Susceptibility of the Novel Superconducting Compound $N a_{0.35} C o O_{2} \cdot 1.3 H_{2} O$