Characterization of magnetic oxide recording media using fourier analysis of static hysteresis loops

A technique for characterizing the entire static hysteresis loop using Fourier analysis has been developed. The method goes beyond the familiar listing of saturation moment, squareness, coercivity, and switching field distribution to describe the magnetization process in detail. The essence of the technique is to "unfold" the static hysteresis loop by plotting the moment as a function of applied field over one complete field cycle and then to take the Fourier transform of the resulting waveform. The procedure is repeated for a series of minor loops taken with increasing values of maximum field until saturation is achieved and the dependence of the harmonic content on maximum field is used to differentiate among various oxide recording media. Several additional applications of the Fourier transform method, including characterization of the temperature dependence of hysteretic properties and analytic expressions for accurate loop reconstruction, are described.