Advertisement

Structural and Magnetic Properties of Fine γ-Fe2O3 Particles

  • M. P. Morales
  • M. Ocaña
  • T. Gonzalez-Carreño
  • C. J. Serna
Part of the NATO ASI Series book series (ASHT, volume 12)

Abstract

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).

Keywords

Coercive Force Spray Pyrolysis Axial Ratio Nanometer Size Ammonium Citrate 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Matijevic, E. (1993) Preparation and properties of uniform size colloids, Chem. Mater. 5, 412CrossRefGoogle Scholar
  2. 2.
    Morales, M. P., Pecharromán, C., González-Carreño T. and Serna, C. J. (1994) Structural characteristics of uniform γ-Fe2O3 particles with different axial (length/width) ratios, J. Solid State Chem. 108, 158 - 163CrossRefGoogle Scholar
  3. 3.
    Matijevic, E. and Scheirrer P. (1978) Ferric hydrous oxide sols. III. Preparation of uniform particles by hydrolysis of Fe (III)-chloride, -nitrate and -perchlorate solutions, J. Colloid and Interface Sci. 63, 509 - 524CrossRefGoogle Scholar
  4. 4.
    Ozaki, M, Kratohvil, S and Matijevic, E. (1984) Formation of monodispersed spindle type hematite particles, J. Colloid and Interface sci. 102, 146–151CrossRefGoogle Scholar
  5. 5.
    González-Carrerño, T., Morales, M. P., Gracia, M. and Sema, C. J. (1993) Preparation of uniform γ-Fe2O3 particles with nanometer size by spray pyrolysis, Mater. Letters 18, 151 - 155CrossRefGoogle Scholar
  6. 6.
    Morales, M. P., González-Carreño, T. and Sema, C. J. (1992) The formation of α-Fe2O3 monodispersed particles in solution, J. Mater. Research 7, 2538 - 2545CrossRefGoogle Scholar
  7. 7.
    Ocaña, M., Rodríguez-Clemente R. and Sema, C. J. (1995) Uniform colloidal particles in solution: Formation mechanism, Advan. Mater. 7, 1006 - 1011Google Scholar
  8. 8.
    Ocaña, M., Morales M. P. and Sema, C. J. (1995) The growth mechanism of α-Fe203ellipsoidal particles in solution, J. Colloid Interface Sd. 171, 85 - 91CrossRefGoogle Scholar
  9. 9.
    Andrés-Vergés, M., Mifsuf A. and Sema, C. J. (1990) Formation of rod-like zinc oxide microcrystals in homogeneous solutions, J. Chem. Soc. Faraday Trans. 86, 959 - 963CrossRefGoogle Scholar
  10. 10.
    Morales, M. P., de Julián, C., González J. M. and. Sema, C. J (1994) The effect of the distribution of vacancies on the magnetic properties of γ-Fe2O3 particles, J. Mater. Res. 8, 135 - 141CrossRefGoogle Scholar
  11. 11.
    Morales, M. P., de Julián, C., Sema, C. J and. González J. M. (1994) Magnetic viscosity of uniform γ-Fe2O3 particles with different degrees of cationic ordering, JEFF Trans. Magn. 30, 772–774CrossRefGoogle Scholar
  12. 12.
    Ohmori M. and Matijevic, E. (1992) Preparation and properties of uniform coated colloidal particles. VII. Silica on hematite, J. Colloid and Interface Sci. 150, 594 - 598CrossRefGoogle Scholar
  13. 13.
    Tronc, E., Prene, P., Jolivet, J. P., d’Orazio, F., Lucari, F., Fiorani, D., Godinho, M., Cherkaoni, R., Nogues, M. and Dorman J. L. (1995) Magnetic behaviour of nanoparticles by Mössbauer spectroscopy and magnetic measurements, Hyper. Inter. 95, 129 - 148CrossRefGoogle Scholar
  14. 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

Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • M. P. Morales
    • 1
  • M. Ocaña
    • 1
  • T. Gonzalez-Carreño
    • 1
  • C. J. Serna
    • 1
  1. 1.Institute de Ciencia de Materiales de MadridCSICMadridSpain

Personalised recommendations