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Iron cobaltite powders Co x Fe 3 À x O 4 (1 r xr 2.46) were synthesized with compositions in between the cobalt ferrite CoFe 2 O 4 and Co 2.46 Fe 0.54 O 4. The cationic distribution of pure spinel phases was determined by Mössbauer spectroscopy: as Co content increases in the spinel oxide, Co 3 þ cations replace Fe 3 þ cations in the octahedral sites and Co 2 þ cations migrate from octahedral to tetrahedral sites. Saturation magnetizations M S measured at 5 K by a SQUID magnetometer were consistent with the values calculated from the cationic distribution. M S decreases as diamagnetic Co 3 þ cations replace strongly magnetic Fe 3 þ cations. Two spinel phases were formed by spinodal decomposition of Co 1.73 Fe 1.27 O 4 phase submitted to a subsequent thermal treatment, one with a high amount of iron Co 1.16 Fe 1.84 O 4 and one other containing mostly cobalt Co 2.69 Fe 0.31 O 4. Increase of the experimental M S value obtained after the spinodal decomposition is in accordance with the calculated value deduced from the cationic distribution of the two phases.

Das durch 1:1‐molare Umsetzung des Diols (I) mit dem Phosphin (II) gebildete bicyclische Phosphin (III) dimerisiert spontan unter Spaltung und Neubildung zweier P‐O‐Bindungen zu dem einzigen Produkt (IV).

Co1.7Fe1.3O4 thin films are submitted to spinodal transformation after annealing at low temperature.

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Sputtering deposition of spinel ferrites leads to a combination of attractive physical properties (optical, magnetic, and semiconducting), which can be adjusted by carefully selecting the preparation conditions and stoichiometry during controlled postdeposition annealing. Thin-sputtered ferrite films are of great interest for integration as functional parts in microsystems. In this paper, we report the effect on electrical properties of the microstructure of sputtered zinc-ferrite films. Transmission electron microscopy and atomic force microscopy were used to observe these nanostructured layers. The measured surface area to projected surface area ratio was calculated on the basis of Brunauer-Emmett-Teller measurements with krypton at 77K. The contribution of grains and boundaries to the global resistivity of the ferrite films was studied by spectroscopic impedance measurements. Impedance variations were in agreement with the microstructure evolution when the argon deposition pressure was increased. The increase of film dc resistivity versus annealing temperatures was explained by the influence of the microstructure on Fe2+ cation oxidation.

Majority of the authors report elaboration of iron oxide thin films by reactive magnetron sputtering from an iron target with Ar-O 2 gas mixture. Instead of using the reactive sputtering of a metallic target we report here the preparation of Fe 1-x O thin films, directly sputtered from a magnetite target in a pure argon gas flow with a bias power applied. This oxide is generally obtained at very low partial oxygen pressure and high temperature. We showed that bias sputtering which can be controlled very easily can lead to reducing conditions during deposition of oxide thin film on simple glass substrates. The proportion of wustite was directly adjusted by modifying the power of the substrate polarization. Atomic force microscopy was used to observe these nanostructured layers. Mössbauer measurements and electrical properties versus bias polarization and annealing temperature are also reported.

There is a miscibility gap in the CoFe2O4–Co3O4 phase diagram in which the oxides can be subjected to a spinodal transformation.