Influence of interparticle interactions on the Magnetic Properties of Nanosized Maghemite Particles

M.J. TUEROS; L.A. BAUM; R.A. BORZI; S.J. STEWART; R.C. MERCADER; S.G. MARCHETTI; J.F. BENGOA; L.V. MOGNI

Panamá, Panamá

Conferencia; Octava Conferencia Latinoamericana Sobre Aplicaciones del efecto Mössbauer, LACAME 2002.; 2002

The control of magnetic properties of nanosized ferrimagnetic systems is of great technological and basic importance. For this reason, there is a great effort towards the thorough understanding of their physics and chemistry. However, the ways in which different parameters, like the blocking temperature and the interparticle interactions, depend on the hystory and preparation method are still not fully understood. In this work we report the characterization of the properties of a system of maghemite (g-Fe2O3) nanosized particles prepared by a microemulsion method using an ionic surfactant. The Mössbauer spectra at temperatures from 21 to 295 K demonstrate how the spectra evolve from a totakky magnetically split signal at low temperatures to a single superparamagnetic doublet at 295 K. An average particle size of 6.8 nm was obtained from the Mössbauer blocking temperature (150K). The current results, with narrow range of temperatures in which the splitting takes place – compared with other nanoparticles systems – indicate that the particles have a sharp size distribution. AC Susceptibility analyses show a shift of the maximum of the susceptibility compatible with a system of interacting particles