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

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 pm of natural magnetite, titanomagnetite and hematite.From these cuwes, the remanent acquisition coercive force Hi,, the remanent coercive force H,, and the median destructive field of IRM Hy21 were determined.Theoretically these parameters should be the same for an assembly of non-interacting, homogeneously distributed, randomly oriented singledomain grains.For a given hematite specimen Hi,, Ha and HhI 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 Hi, is larger than Ha which again is larger than HI/^.However, the ratios Hir/Ha and HhI/Ha 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 pm, independently of grainsize, quantity and packing density of the magnetic material, is: