High-sensitivity vibrating reed studies of superconductors

Recent improvements in the vibrating reed (VR) technique permit precision studies of the mixed state of complex superconducting materials far below the upper critical magnetic field H(c2) VR data for thin film, crystalline and ceramic (Ba(0.6)K(0.4))BiO(3) samples demonstrate the sensitivity of the VR to microstructure and inhomogeneities, and a study of HoNi(2)B(2)C reveals previously inaccessible vortex dynamical anomalies and minute details of a complex phase competition between magnetism and reentrant superconductivity. CeRu(2) VR data are reversible near H(c2) where giant hysteresis is observed in DC magnetization data, but are hysteretic over an extended region at lower temperatures and fields, indicating vortex dynamics must be considered in testing the existence of unconventional pairing states proposed for this system.