Grain-size dependence of anhysteresis in iron oxide micropowders

The low-field anhysteresis of small equidimensional multidomain particles of Fe
3
O
4
is found to be surprisingly large. For particle sizes below about 0.075 μm the anhysteretic susceptibility equals or surpasses that of elongated or doped equidimensional single-domain γFe
2
O
3
particles used in conventional recording tapes.