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

Abstract

We succeeded in synthesizing the powder samples of bilayer-hydrate sodium cobalt oxide superconductors NaxCoO2-yH2O with Tc = 0 ~ 4.6 K by systematically changing the keeping duration in a 75 % relative humidity atmosphere after intercalation of water molecules. From the magnetic measurements, we found that the one-day duration sample does not show any superconductivity down to 1.8 K, and that the samples kept for 2 ~ 7 days show superconductivity, in which Tc increases up to 4.6 K with increasing the duration. Tc and the superconducting volume fraction are almost invariant between 7 days and 1month duration. The 59Co NQR spectra indicate a systematic change in the local charge distribution on the CoO2 plane with change in duration.

arXiv comment4 pages, 5 figures, submitted to Journal of the Physical Society of Japan

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Cited by in corpus (4)

• Possible Spin-triplet Superconductivity in NaxCoO2yH2O - 59Co NMR Study
• 59Co Nuclear Quadrupole Resonance Studies of Superconducting and Non-superconducting Bilayer Water Intercalated Sodium Cobalt Oxides NaxCoO2.yH2O
• Magnetic anomalies of hydrous cobaltate compound Na_x(H_3O)_zCoO_2 \cdot yH_2O detected by NMR and NQR measurements
• 23Na NMR study of non-superconducting double-layer hydrate NaxCoO2.yH2O