Lower critical fields Hcl of sintered samples of high-Tc Cu oxides have been measured as a function of temperature T. The diamagnetic moments M of the La2-xSrxCuO4 samples and a crystal specimen of YBa2Cu3O7-δ have also been measured in detail after cooling in the applied magnetic field H, with constant H and with increasing T. The T-dependence of Hcl has been found to be quite anomalous. The plot of |M| against H at constant T is also anomalous, that is, at low temperatures |M| increases with H in the very high field region far above Hcl. It is observed in both field directions, parallel and perpendicular to the CuO2 plane. These two kinds of anomalies are found to have the same origin. They may indicate the existence of the significant difference of the superconducting properties between the high-Tc oxides and usual superconductors.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Materials Chemistry