Anomalous flux pinning in beta-pyrochlore oxide superconductor KOs2O6

摘要

The superconducting transition of the beta-pyrochlore oxide KOs2O6 with T-c = 9.60 K is studied by resistivity measurements under various magnetic fields using a high-quality single crystal. The reentrant behavior of superconductivity is observed near T-c in low magnetic fields below 2T. The recovered resistance probably due to flux flow exhibits an anomalous angle dependence, indicating that flux pinning is enhanced in magnetic fields along certain crystallographic directions such as [110], [001], and [112]. It is suggested that there is an intrinsic pinning mechanism coming from the specific crystal structure of the beta-pyrochlore oxide.