Abstract
We report magnetic-field-dependent magnetization and microwave impedance measurements on a superconductor prepared by high-pressure synthesis. We find that the upper critical field is linearly dependent on temperature near and the dc irreversibility field exponent is ∼1.4. Microwave surface impedance measurements were carried out in applied magnetic fields up to 8 T. The low-field data show an absence of weak links in the superconducting state. By inverting the surface impedance data, we find a vortex depinning frequency that decreases with increasing magnetic field, which is characteristic of collective pinning.
- Received 17 July 2001
DOI:https://doi.org/10.1103/PhysRevB.66.014505
©2002 American Physical Society