The dependence of magnetic parameters on the mixing proportion of hematite and magnetite

In this study,magnetic measurements were conducted on two series of hematite and magnetite mixtures,with the purpose to study the response of magnetic parameters to the mixture of magnetic minerals with different coercivities.Series 1 and 2 were formed by mixing 0.3% superparamagnetic and pseudo-single-domain magnetite with varying proportions(0~9%) of hematite in a CaCO3 matrix,respectively.S ratios and Hcr/Hc,which are sensitive to the mixture of magnetic minerals with different coercivities,and are also impacted by the grain size of magnetite.S ratios of series 1 decline more dramatically than those of coarse-grained series 2 when the content of hematite is less than 2%.For series 1,Hcr/Hc ratios display larger variations when the hematite content is more than 3%.The results demonstrate that the widely used magnetic grain size indicators χARM/χ and χARM/ SIRM are also influenced by the proportions of ferrimagnetic versus antiferromagnetic minerals.For series 1 with fine-grained magnetite,χARM/SIRM shows an evident decline with increasing hematite content up to 3%.Meanwhile,this study indicates that there should be cautions in the interpretations of magnetic parameters.The influence of magnetite grain size on the coercivity indicators should be properly addressed,especially in the case of mixtwre composed of superparamagnetic magnetite and hematite.