LOW-FREQUENCY MAGNETIC MEASUREMENTS ON HIGH-TC SUPERCONDUCTING MATERIALS

This paper deals with experimental techniques based on analysis of macroscopic magnetic properties of a superconductor placed in a magnetic field varying harmonically with time. Contactless ways of inducing the current into the sample are particularly advantageous in the case of ceramic high-T(c) superconductors. Common features of methods utilizing various instrumentation are discussed, as well as differences between models used to determine the parameters characterizing the superconducting material. The usefulness of low-frequency magnetic measurements is demonstrated on a practical example of polycrystalline YBa2Cu3O(x). Some experimental facts open for theoretical explanation are presented in the last section.