Microstructure, relaxation, and print-through in γ-Fe2O3 particles

Four samples of γ-Fe2O3 representing a range of Hc, particle size, and print-through behavior were examined for their structure. All particles were single crystals with symmetric cross sections and predominant [110] longitudinal axis orientation. The sizes obtained from x-ray line broadening measurements were shown to relate to average particle diameters rather than average crystallite sizes within a particle. Neither Hc nor print-through seemed to correlate with porosity as determined from TEM. Print-through (PT) was highest in the sample with the smallest average particle size. This suggests that print-through is strongest in samples with the largest fraction of particles small enough to show magnetization instability. The data for some samples were not completely consistent with this view. The sample with the highest print-through also had the largest concentration of anti-phase boundaries (APB). The manner in which APB’s can lower the threshold for magnetization instability, thereby increasing print-through, is discussed.