Abstract
Superparamagnetic magnesioferrite particles were precipitated from MgO containing approximately 1 cation % Fe, by aging at 700° and 800°C. The composition was determined to be Mg1.2Fe1.8O3.9 and the spontaneous magnetization at 0°K was 330 emu cm−3. The cation distribution and Curie temperatures were found to depend only on aging temperature, and not on aging time or solution‐treating temperature. Curie temperatures of 520° and 490°K were measured on samples aged at 700° and 800°C, and the fraction of iron ions on tetrahedral sites within the precipitate was 0.36 and 0.35, respectively. The saturation magnetization is higher, the Curie temperature is lower, and the fraction of iron ions on tetrahedral sites is less than in bulk stoichiometric MgFe2O4.

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