Recently, the application of nanosized magnetite particles became an area of growing interest for their potential practical applications. Nanosized magnetite samples of 36 and 9 nm sizes were synthesized. Special care was taken on the right stoichiometry of the magnetite particles. Mössbauer spectroscopy measurements were made in 4.2-300 K temperature range. The temperature dependence of the intensities of the spectral components indicated size dependent transition taking place in a broad temperature range. For nanosized samples, the hyperfine interaction values and their relative intensities changed above the Verwey transition temperature value of bulk megnetite. The continuous transition indicated the formation of dendritelike granular assemblies formed during the preparation of the samples.

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Thin 57 Fe layers evaporated onto an MgO(100) single-crystal substrate and covered by an evaporated MgO layer were studied by low-temperature conversion electron Mössbauer spectroscopy. The temperature dependence of the spectra indicates superparamagnetic behavior below 8 ML nominal thickness of the Fe layer signaling a cluster-type growth mode. The low-temperature hyperfine fields are consistent with a model that defines two types of metallic Fe atoms: bulklike and interfacial ones. Formation of FeO or (Fe,Mg)O at the interface layer is not observed. The sample with a 4-ML Fe layer when grown over a cleaved MgO substrate shows almost perfect perpendicular magnetization, as locally probed at 15 K by the hyperfine magnetic field, while random magnetization orientation and lower blocking temperature is observed in the case of a polished substrate. The perpendicular anisotropy observed at low temperature is attributed to mechanical stresses arising from the epitaxial relation and the different temperature dilatation of the subsequent layers.

ϵ‐Fe2O3 is a phase distinct from other iron oxides and hydroxides. It is antiferromagnetic with TN = 480 °K, and it converts to α‐Fe2O3 at 1040 °K. Mössbauer spectra and magnetic properties of the crystallites studied suggest fine particle behaviour, with a large concentration of vacancies. The magnetically split Mössbauer spectrum has broad lines, even at 4.2 °K, where Hhf = (500 ± 5) kOe, δ = (0.7 ± 0.1) mm/s relative to chromium and 2 ϵ = (0.4 ± 0.1) mm/s.