INTECIN   20395
INSTITUTO DE TECNOLOGIAS Y CIENCIAS DE LA INGENIERIA "HILARIO FERNANDEZ LONG"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Controlled tuning of magnetic interactions in silica-covered iron oxide nanoparticle
Autor/es:
MOSCOSO LONDOÑO, OSCAR; TANCREDI, PABLO; RIVAS, PATRICIA; SOCOLOVSKY, LEANDRO M.
Lugar:
Buenos Aires
Reunión:
Simposio; Frontiers in physical sciences; 2016
Institución organizadora:
International Center for Advanced Studies(ICAS), Max Planck Liason Office for Latin America, in cooperation with the Kolleg Programme of the Alexander von Humboldt Foundation
Resumen:
When studying the magnetic properties of nanoparticles in real samples, being able to disjoin the effects of interactions from the effects of size, shape and anisotropy easy axis distributions is a big challenge. For this purpose, nearly monodisperse iron oxides nanoparticles were synthesized by high temperature thermal decomposition of organic precursors and then coated with SiO2 through the inverse microemulsion method, employing tetraethyl orthosilicate (TEOS) in different amounts and for different reaction times in order to tune the silica shell thickness. TEM images and SAXS measurements corroborate the formation of core-shell structures with quite uniform sizes and shapes, for the cores an asymmetrical size distribution with mean diameter of 7.45nm was obtained with a standard deviation of 1.96nm, and shells that range from a few nanometers to 20nm.Regarding this characterization, magnetic features as a function of external field, temperature and AC susceptibility, were analyzed. Typical characteristics of superparamegnetic systems were observed, with gradually increasing interactions tendencies: shift in the blocking temperature (TB) to higher temperatures, broadening of the ZFC curve, decrease in the FC magnetization below TB, etc. The shift in the maxima of the out of phase component of the AC susceptibility was analyzed with the Vogel-Fulcher model and relates to different relaxation times for each sample, also associated with the effect of interactions on the relaxation processes.