Article ID Journal Published Year Pages File Type
1820080 Physica C: Superconductivity and its Applications 2007 4 Pages PDF
Abstract

Nuclear quadrupole frequency (νQ) and spin-lattice relaxation rate 1/T1 of Co were measured on various bilayered hydrate (BLH) NaxCoO2 · yH2O (y ∼ 1.3) with different values of superconducting (SC) and magnetic-transition temperatures, Tc and TM, together with non-SC monolayered hydrate (MLH) NaxCoO2 · yH2O (y ∼ 0.7). In the temperature range above 70 K, 1/T1T in all samples follows the similar temperature dependence as each other. In the BLH compounds, 1/T1T is enhanced with decreasing temperature below 70 K, and the values of 1/T1T at Tc are larger in the higher-ν3 sample, where ν3 is the peak frequency of the NQR spectrum arising from ±5/2 ↔ ±7/2 transitions. The magnetic ordering is indicated from the prominent divergence of 1/T1T at TM and the presence of the internal field at the Co nuclear site in the samples with ν3 higher than 12.5 MHz. We analyze the temperature dependence of 1/T1T in all samples on the basis of identical formula, and discuss the relationship between magnetic fluctuations and superconductivity in the BLH cobaltate.

Related Topics
Physical Sciences and Engineering Physics and Astronomy Condensed Matter Physics
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