Influence of crystallite size and shape on the viscous magnetization of λ-Fe2O3 particles

Abstract The usefulness of the normalized thermal fluctuation field in magnetic granulometry is confirmed with data for λ-Fe 2 O 3 and CrO 2 . The variation of the normalized fluctuation field with crystallite diameter in the λ-Fe 2 O 3 follows a similar trend for both isometric and longitudinal crystallite growth even though in the second case the diameter is not a good guide to the volume of the crystallites. This suggests that the smallest dimension of the crystallite rather than its volume is critical for the activation volume; after correction for the differences in coercivity a long, thin particle is more subject to thermal activation than a short, thick one of the same volume.