Alternating and rotational hysteresis losses of γ-Fe2O3powders in a nonmagnetic matrix

Some aspects of the alternating and rotational hysteresis losses of very diluted samples of γ-Fe2O3particles are examined. The packing fractionpof the particles ranges from 0.001 to 0.120. The coercive force is found to be independent ofp. The alternating and rotational hysteresis losses appear dependent uponpforp < 0.04; the rotational losses increase considerably aspapproaches zero. The values of the rotational hysteresis integral are close to the theoretical ones corresponding to the model of magnetization reversal of chain of spheres with fanning, but they increase slightly with decreasingpforp < 0.04. Generally, the ratio of rotational to alternating losses is about twice that for bulk materials. All these effects are ascribed to a weakening of the magnetic interactions among particles.