AC Magnetic Susceptibility Technique for the Characterization of High Temperature Superconductors

Abstract

The absolute magnetic susceptibility as a function of temperature with different amplitude and frequency of the applied field is used to characterize the magnetic properties of high T c-superconductors. In the present work our design of a laboratory-built ac susceptometer based on the mutual inductance method using local facilities is demonstrated and tested. The setup have moment precision of better than 7×10-10 A.m 2. The real, or in-phase, component and the imaginary, or out of-phase, component of the complex susceptibility were measured independently applying a computer program designed specially for this purpose. YBa 2 Cu 3 O 7-x high temperature ceramic superconductor was used to test and calibrate the system. The formulas for susceptibilities corresponding to the models of linear diffusion and critical state are used in the recognition of the mechanism controlling the flux dynamics and in the determination of the superconducting properties for YBa 2 Cu 3 O 7-x and EuBa 2 Cu 3 O 7-x. Superconducting properties such as, critical temperature, T c-onset , critical current density, J c , and electrical resistivity were calculated from the experimental data.