Superconducting to spin-glass state transformation in β-pyrochlore K_xOs₂O₆

β-pyrochore KOs₂O₆, which shows superconductivity below ∼9.7 K, has been converted into K_xOs ₂O₆ (x 23-12) electrochemically to show spin-glass-like behavior below ∼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.