Anisotropy field distribution in amorphous ferromagnetic alloys from second harmonic response

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Abstract
We present a new procedure to obtain the anisotropy distribution in a ferromagnetic amorphous alloy. The method is based on the existence of second‐order harmonics in the differential magnetization around the anisotropy field. We derive a mathematical expression relating the strength of the second‐harmonic component and the anisotropy distribution function. An experimental setup is described and the optimum operating conditions discussed. The apparatus is based on the detection of the voltage induced in a coil using a lock‐in amplifier tuned to a frequency double to the exciting one. Results obtained on a stress annealed sample show the existence of well defined values of the anisotropy in addition to a continuous background.