Determination of field-independent and field-dependent components of anisotropy of susceptibility through standard AMS measurement in variable low fields I: Theory

Three methods were developed for simultaneous determination of the field-independent susceptibility tensor and the initial susceptibility tensor of MD ferromagnetic fraction, all based on standard measurement of the AMS in variable fields within the Rayleigh Law range. The former tensor reflects possible effects of diamagnetic and paramagnetic minerals, pure magnetite, SD ferromagnetic minerals, and initial susceptibility of MD ferromagnetic minerals. The initial susceptibility tensor of MD ferromagnetic fraction does not however reflect the effect of the entire fraction, because the effect of the SD sub-fraction contributes to the field-independent susceptibility tensor. The differences in the degree of AMS of the field-independent susceptibility tensor and that of the initial susceptibility tensor of MD ferromagnetic fraction may be useful in magnetic granulometry.