59Co Nuclear Quadrupole Resonance Studies of Superconducting and Non-superconducting Bilayer Water Intercalated Sodium Cobalt Oxides NaxCoO2.yH2O

Abstract

We report 59Co nuclear quadrupole resonance (NQR) studies of bilayer water intercalated sodium cobalt oxides NaxCoO2.yH2O (BLH) with the superconducting transition temperatures, 2 K < T_c <= 4.6 K, as well as a magnetic BLH sample without superconductivity. We obtained a magnetic phase diagram of T_c and the magnetic ordering temperature T_M against the peak frequency nu_3 59Co NQR transition I_z = +- 5/2 <=> +-7/2 and found a dome shape superconducting phase. The 59Co NQR spectrum of the non-superconducting BLH shows a broadening below T_M without the critical divergence of 1/T_1 and 1/T_2, suggesting an unconventional magnetic ordering. The degree of the enhancement of 1/T_1T at low temperatures increases with the increase of nu_3 though the optimal nu_3~12.30 MHz. In the NaxCoO2.yH2O system, the optimal-T_c superconductivity emerges close to the magnetic instability. T_c is suppressed near the phase boundary at nu_3~12.50 MHz, which is not a conventional magnetic quantum critical point.

arXiv comment4 pages, 5 figures

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• Novel phase diagram of superconductor NaxCoO2-yH2O in a 75 % relative humidity

Cited by in corpus (12)

• A unified origin for the 3D magnetism and superconductivity in Na${}_x$CoO${}_2$
• Deformation of Electronic Structures Due to CoO6 Distortion and Phase Diagrams of NaxCoO2.yH2O
• CoO2-Layer-Thickness Dependence of Magnetic Properties and Possible Two Different Superconducting States in NaxCoO2.yH2O
• Co-NMR Knight Shift of NaxCoO2 \dot yH2O Studied in Both Superconducting Regions of the Tc-nuQ3 Phase Diagram Divided by the Nonsuperconducting Phase
• Specific Heat and Superfluid Density for Possible Two Different Superconducting States in NaxCoO2.yH2O
• Dynamical magnetic susceptibility in the lamellar cobaltate superconductor Na_xCoO_2$\cdot y$H_2O
• 59Co, 23Na, and 1H NMR Studies of Double-Layer Hydrated Superconductors NaxCoO2-yH2O
• Doping dependence of Meissner effect in triangular-lattice superconductors
• Thermodynamic properties in triangular-lattice superconductors
• Magnetic anomalies of hydrous cobaltate compound Na_x(H_3O)_zCoO_2 \cdot yH_2O detected by NMR and NQR measurements
• In-plane Anisotropy of the Magnetic Fluctuations in NaxCoO2-yH2O
• Asymmetric doping dependence of superconductivity between hole- and electron-doped triangular-lattice superconductors