In order to evaluate the strength of intergrain coupling, which determines the transport critical-current of polycrystalline oxide superconductors, we have studied the relation between the transport critical-current and the spatial distribution of the magnetic flux density for YBaCuO thin films as well as bulk superconductors. We have measured the profile of the magnetic flux trapped inside bulk YBaCuO samples with a small Hall magnetic sensor, and revealed the corelation between critical current densities and the slope of the trapped-flux profile, as can be described by the critical state model. The measurement of the magnetic-field penetraion depth of YBaCuO thin films in a Meissner state is also carried out by measuring of the loop inductance of a DC SQUID which is placed on the YBaCuO thin film to be measured. Observed magnetic-field penetration depths of polycrystalline films with thicknesses of 1-3m deposited on Mg0 singlecrystal substrates amount to ~lm for samples with Telend 80K and the critical current density jc~10-A/cm at 4.2K.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering