Precipitation of nanopowders with mixed magnetite–maghemite composition was carried out under different conditions and with different separation techniques. The exact character of interactions of different iron oxide phases in the nanopowder was the main object of interest. The obtained nanopowders have spherical particles about 10–20 nm in size. Electron paramagnetic resonance (EPR) study showed that iron ions incorporate fully into magnetite and maghemite structures. The shape of the EPR line points out that single homogenous solid solutions were formed during synthesis. In the studied solid solutions, different ratios of vacancies and Fe2+/Fe3+ ratios were observed but in spite of different synthesis techniques in both cases, there were no additional diamagnetic structural phases presented.
