Autocalibrating quasistatic M-H hysteresis loop tracer with negligible drift

A computer-controlled system for measuring M-H hysteresis loops of soft magnetic materials is described. It overcomes many of the problems associated with these kinds of measurements of low coercivity materials. The combination of ‘‘low drift’’ hardware and measurement procedure makes software correction unnecessary. At every field step, the homemade integrator is reset in order to minimize the drift and to provide a way of separating the sample contribution to the signal from the field contribution and, consequently, to allow M-H plots. Furthermore, to avoid the residual drift of the hardware, the method of ‘‘two-way measurement’’ is applied, giving drifts of 0.01% per hour. Results obtained for a FINEMET alloy film annealed at different temperatures are presented, illustrating the ability of the system to measure soft magnetic materials.