Superconducting to spin-glass state transformation in beta-pyrochlore KxOs2O6

Abstract

beta-pyrochore KOs2O6, which shows superconductivity below similar to 9.7 K, has been converted into KxOs2O6 (x less than or similar to 2/3-1/2) electrochemically to show spin-glass-like behavior below similar to 6.1 K. A room-temperature sample surface potential versus charge transfer scan indicates that there are at least two two-phase regions for x between 1 and 0.5. A rattling model of superconductivity for the title compound has been examined using electrochemical potassium de-intercalation. The significant reduction of superconducting volume fraction due to minor potassium reduction suggests the importance of defect and phase coherence in the rattling model. Magnetic susceptibility, resistivity, and specific heat measurement results have been compared between the superconducting and spin-glass-like samples.