Shape Distribution of Magnetic Powders

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Abstract
In work reported earlier, the average length‐to‐diameter ratios determined magnetically did not agree with those observed under the electron microscope; this was thought due to magnetic interactions. This paper describes further shape determination measurements on γ‐Fe2O3 samples of increasing dilution by the original method and by two analogous methods described by Wohlfarth. The results show a slight increase of mean length‐to‐diameter ratio with dilution and a considerable broadening of the distribution toward large length‐to‐diameter ratios. The different methods of measurement described do not yield the expected congruent curves at very low concentration. This indicates a deviation from Stoner‐Wohlfarth rotation in these particles. The details of the mathematical methods are also described.