Relationship between median destructive field and remanent coercive forces for dispersed natural magnetite, titanomagnetite and hematite


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    Earth Physics Branch, Energy, Mines and Resources, 1 Observatory Crescent, Ottawa, Ontario K1A OY3, Canada.


Summary. Remanent acquisition curves, remanent hysteresis curves and alternating field demagnetization curves were determined for a number of artificial rock specimens containing well-defined grain-size fractions between 5 and 250 μm of natural magnetite, titanomagnetite and hematite. From these curves, the remanent acquisition coercive force H'cr, the remanent coercive force Hcr and the median destructive field of IRM H½I were determined. Theoretically these parameters should be the same for an assembly of non-interacting, homogeneously distributed, randomly oriented single-domain grains. For a given hematite specimen H'cr, Hcr and H½I have about the same value in spite of the strong grain-size dependence of these parameters. For each specimen of magnetite and titanomagnetite the value of H'cr is larger than Hcr which again is larger than H½I. However, the ratios H'cr/Hcr and H½I/Hcr appear to have a (different) constant value. An interesting relationship which appears to hold for dispersed magnetite, titanomagnetite or hematite grains between 5 and 250 μm, independently of grain-size, quantity and packing density of the magnetic material, is: