Structural and Magnetic Properties of Fine γ-Fe2O3 Particles
The magnetic properties of γ-Fe2O3 uniform particles prepared by two different methods; from α-Fe2O3 precursors obtained by homogenous hydrolysis and directly, by spray pyrolysis of iron salt solutions, are analysed and related to their structural characteristics. In the first case, the γ-Fe2O3 particles, obtained by reduction-oxidation from the corresponding α-Fe2O3 precursors, showed different degrees of order in the vacancies distribution depending on the presence of defects inside the α-Fe2O3 particles. It is shown that both the saturation magnetisation and the coercive force decrease with increasing the disorder distribution of the vacancies in γ-Fe2O3.
The spray pyrolysis method can produce directly γ-Fe2O3 particles with nanometer size and different states of aggregation depending on the used precursor salt. These particles were found to be superparamagnetic with an unusually low blocking temperature. The influence of the size and the geometry of the aggregates is discussed in terms of ac magnetic susceptibility (χac).
KeywordsCoercive Force Spray Pyrolysis Axial Ratio Nanometer Size Ammonium Citrate
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- 7.Ocaña, M., Rodríguez-Clemente R. and Sema, C. J. (1995) Uniform colloidal particles in solution: Formation mechanism, Advan. Mater. 7, 1006 - 1011Google Scholar
- 14.López, F. J. Lázaro, A., González-Carreño, T., Morales, M. P. and Sema, C. J. (1995) Magnetic properties of γ- Fe2O3 small particles prepared by spray pyrolysis, IFFY Trans Magn. 140–144, 383–384Google Scholar