FOURIER-ANALYSIS OF DIGITAL HYSTERESIS DATA - ROCK MAGNETIC APPLICATIONS

The approach to saturation of a ferromagnetic material can be characterized in terms of the frequency content of its hysteresis loop. This is done by 'unfolding' the loop into a pseudo-waveform, which is then analyzed using standard Fourier methods. In experiments on samples with discrete grain sizes of magnetite, the decay of Fourier component amplitude as a function of harmonic degree is sensitive to grain size (which controls the 'squareness' of the loop). For samples containing a mixture of magnetite grain sizes, and for samples containing a mixture of magnetite and hematite, the phase shift as a function of harmonic degree is a sensitive indicator of the distribution of coercivities (which controls the asymmetry of the unfolded waveform).