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 Tc – 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.m2. 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. YBa2Cu3O7-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
YBa2Cu3O7-x and EuBa2Cu3O7-x. Superconducting properties such as, critical
temperature, Tc-onset, critical current density, Jc, and electrical resistivity were
calculated from the experimental data.