Magnetic Nature of Water Intercalated Na0.35CoO2

Abstract

Abstract In order to clarify the carrier density dependence of the microscopic magnetic nature in Na x CoO 2 * y H 2 O, we have performed a μ + SR study of H 2 O and D 2 O absorbed samples. Based on the ZF- μ + SR measurements, there was no clear difference between the two superconducting phases (SCI and SCII). This is also likely to exclude the exotic scenario for the superconductivity of the SCII phase, in which the superconducting state breaks the time-reversal symmetry of the Cooper pairs, resulting in the appearance of a weak internal magnetic field below T c . Furthermore, the ZF-spectrum for the H 2 O absorbed sample exhibits a clear oscillation in the whole T range measured (1.4-100 K), suggesting the formation of “[H 3 O] + -like” H 2 μ + O ions in the sample. The absence of the oscillation in the D 2 O absorbed sample also evidences the presence of the H 2 μ + O complex. Considering the fraction of the H 2 μ + Osignal, we have demonstrated the coexistence of [H 3 O] + ions and H 2 O in this compound. Finally, the muonic Knight shift measurements suggested the change in electronic state around 10 K and 40 K for the SCI and SCII samples.