AUTOCALIBRATING QUASI-STATIC M-H HYSTERESIS LOOP TRACER WITH NEGLIGIBLE DRIFT

A computer-controlled system for measuring M-H hysteresis loops of sof t magnetic materials is described. It overcomes many of the problems a ssociated 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 homema de integrator is reset in order to minimize the drift and to provide a way of separating the sample contribution to the signal from the fiel d contribution and, consequently, to allow M-H plots. Furthermore, to avoid the residual drift of the hardware, the method of ''two-way meas urement'' is applied, giving drifts of 0.01% per hour. Results obtaine d for a FINEMET alloy film annealed at different temperatures are pres ented, illustrating the ability of the system to measure soft magnetic materials. (C) 1996 American Institute of Physics.