Measuring the Hysteresis Loop of Permanent Magnets With the Pulsed Field Magnetometer

We discuss a comprehensive approach to the characterization of permanent magnets with the pulsed field magnetometer. The approach is based on a systematic comparison of the results obtained by this method with those from the conventional closed-circuit and open-sample methods and on the assessment of the dynamic phenomena engendered by the application of the fast exciting field pulse. Such phenomena derive from the thermal fluctuation after effect and the eddy currents, whose contributions to hysteresis loop swelling are brought to light and separately evaluated. We show that the quasi-static hysteresis loop can be retrieved from the dynamically obtained one by compensating for the magnetic viscosity field, found to be proportional to the coercive field, and the eddy-current counterfield. A simple analytical formulation accounts for and predicts the effect of the counterfield.