Studies of magnetic dipolar interaction using different Fe3O4 NPs concentrations in two kind of non-conducting polymer matrices. The role of the chemical nature of coating/matrix ratio

MOSCOSO LONDOÑO, OSCAR ; MURACA, DIEGO; TANCREDI, PABLO; MEIORIN, CINTIA; ARANGUREN, MIRTA I.; MOSIEWICKI, MIRNA A.; PIROTA, KEBLER; SOCOLOVSKY, LEANDRO M.

Joao Pesoa

Encuentro; XIIISBPMat; 2014

The aim of this work was to prepare magnetic nanocomposites in which the iron oxide magnetic nanoparticles distribution within a non-magnetic matrix is adjusted to control magnetic dipolar interactions among them. To achieve this, two kinds of magnetic nanocomposites were prepared, each with different concentrations of Fe3O4 nanoparticles. The first group of samples, called hydrophilic nanocomposites, was prepared using Fe3O4 NPs coated with citric acid, which were dispersed in a polyvinyl alcohol (PVA) matrix. In the other system, called hydrophobic nanocomposites, were used Fe3O4 NPs coated with oleic acid and dispersed in a tung oil/styrene matrix. Through this work, the chemical coating properties and matrix nature are related to the ability of NPs to dispersie into the non-magnetic matrix. Small angle x-ray scattering is used to study those dispersions. Magnetic studies were carried out through Magnetization vs. Applied magnetic field curves which were taken at different temperatures; and Magnetization vs. Temperature ZFC ? FC curves. These experimental data were analyzed by using the interacting superparamagnetic model (ISP) or Allia model [1] that takes into account magnetic interactions of dipolar origin, an excellent agreement whit this model was found in both systems for magnetic nanocomposites with NPs concentration lower than 3 wt%. When the ISP model is used in magnetic nanocomposites with concentrations higher than 3 wt% a spurious results appear as a consequence of stronger-dipolar interactions among Fe3O4 nanoparticles. A proper control of the intensity of dipolar interactions would have positive implication on different biomedical application such as hyperthermia treatment. Recent studies show that such interactions increase the specific absorption rate (SAR) due a crossover between Neel to Brown magnetic relaxation mechanisms.