Phase and structural particularities of nanosized granular inverse spinels

The object of the work were spinel ferroxide nanoparticles of Fe3O4 and CuFe2O4 with Jahn-Teller octahedral distortion. The particles were obtained via a soft chemical process, with the particle size being up to 12 ± 5 nm for Fe3O4 and 6.5 ± 3.5 nm for CuFe2O4. The particles shape was spherical. The crystalline structure and shape evolution of the magnetite particles were investigated by XRD and TEM and compared with properties of particles with larger size. The deviation of the octahedral and tetrahedral voids size radii due to Laplace pressure in the model spinel structire (Fe3O4) as a function of the particle size was observed. The magnetic properties of the particles were studied by means of Moessbauer spectroscopy, vibration sample magnetometer measurements and neutron diffraction. The present study demonstrated that the violation of the ferrospinel's cubic cell symmetry results in a higher probability for the appearance in the very small particles of non-colinearity in the spin magnetic moments ordering. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)