We developed a novel nondestructive and contactless method for measurements of critical current density (Jc) in high-temperature superconductor (HTS) thin films by using a permanent magnet (Sm2Co17). This measurement technique is based on a repulsive force (Fr) and attractive force (Fa) between the magnet and HTS film caused by the shielding currents and pinning forces. The Fr and Fa were measured by using a high-resolution load sensor changing the distance (L) between the magnet and HTS film. An effective maximum repulsive force (F m,eff) could be determined from an extrapolated value of the F r vs. L curve for L = 0 mm. We investigated the relationship of the Jc to theFm,eff in many HTS (YBa2Cu 3O7-δ and ErBa2Cu3O 7-δ) samples. The standard Jc of HTS films was measured by using an inductive measurement system produced from THEVA GmbH. We found that the Jc is almost proportional to the two-thirds power of the Fm,eff normalized by the film thickness. This result indicates that the simple permanent magnet technique can be easily estimate the J c of the HTS films. This system has good reproducibility for the Jc measurements and is useful to provide a rapid, routine characterization of the superconductivity in the HTS materials.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering