CHARACTERIZATION OF THE MAGNETIC DISSIPATION MECHANISM IN A SAMPLE USING INTERMODULATED DETECTION SUSCEPTOMETRY

The flux pinning properties of impure superconducting samples are diff icult to determine. This is due in part to the fact that dissipation o f magnetic energy in a conductive matrix can be mistaken for flux-line flow. Additionally, ferromagnetic contamination can result in hystere sis curves similar to those caused by flux-line pinning. We present a novel solution to this problem, which employs simultaneous irradiation of a sample by two AC magnetic fields of different frequencies. The n on-linear susceptibilities of ferromagnetic and superconducting phases produce intermodulation moments, whereas purely conductive phases pro duce only linear responses to double-frequency irradiation. The interm odulation components of the two non-linear phases are different, allow ing the three phases to be distinguished from each other. We present r esults demonstrating this effect.