High resolution automatic magnetometer using a superconducting magnet: Application to high field susceptibility measurements

Flux creep phenomenon occurs when a magnetic sample is displaced inside a superconducting solenoid. The magnetization measurement by the classical flux integration technique is disturbed by this phenomenon. We describe a method to eliminate this perturbation. At a fixed field, using a special compensated pick-up coil, the measurements, done at regular intervals, tend toward a final value proportional to the moment. Using an integrating digital voltmeter as fluxmeter, the short term reproducibility reaches 2 to 3.10^-6. The apparatus is automatic. It allows measurements such as high field susceptibilities, law of approach to saturation, and anisotropic spontaneous magnetization.