Journal of Materials Science

, Volume 35, Issue 15, pp 3767–3784

CoNi and FeCoNi fine particles prepared by the polyol process: Physico-chemical characterization and dynamic magnetic properties

Authors

  • Ph. Toneguzzo
    • CEA, Le Ripault
  • G. Viau
    • Laboratoire de Chimie des Matériaux Divisés et CatalyseUniversité Paris 7-Denis Diderot
  • O. Acher
    • CEA, Le Ripault
  • F. Guillet
    • CEA, Le Ripault
  • E. Bruneton
    • CEA, Le Ripault
  • F. Fievet-Vincent
    • Laboratoire de Chimie des Matériaux Divisés et CatalyseUniversité Paris 7-Denis Diderot
  • F. Fievet
    • Laboratoire de Chimie des Matériaux Divisés et CatalyseUniversité Paris 7-Denis Diderot
Article

DOI: 10.1023/A:1004864927169

Cite this article as:
Toneguzzo, P., Viau, G., Acher, O. et al. Journal of Materials Science (2000) 35: 3767. doi:10.1023/A:1004864927169

Abstract

Spherical and monodisperse CoxNi100 − x and Fez[CoxNi100 − x]1 − z particles are synthezied by the polyol process over a wide size range (lying from a few micrometers to a few tens of nanometers). The whole physico-chemical characterizations, i.e. dark-field image by TEM, SAED, density, saturation magnetization and chemical analysis, are consistent with a “core-shell” model. In the CoxNi100 − x system, the particles are constituted by a ferromagnetic, almost pure and dense core surrounded by a thin coating composed of metal oxides and metallo-organic phases. On the contrary, in the Fe[CoxNi100 − x]1 − z system, the ferromagnetic core is polycrystalline, slightly porous and retains impurities in higher content, the superficial layer having almost the same composition as in the Co-Ni system, but being twice more thick. The microwave permeability of the CoxNi100 − x and Fez[CoxNi100 − x]1 − z particles, previously insulated by a superficial treatment and then mechanically compacted, is investigated in the 100 MHz-18 GHz frequency range. Whatever the composition, submicrometer-sized particles show several narrow resonance bands which are interpreted as non uniform exchange resonance modes. Iron-based particles have lower resonance frequencies than iron-free powders; they also have higher permeability levels despite their lower cristallinity and their higher impurity content. A mild thermal treatment allows to increase this permeability by eliminating the metallo-organic impurities without modifying the morphology of the particles.

Copyright information

© Kluwer Academic Publishers 2000