The Effect of Submicrometer Clustering on the Magnetic Properties of Free-standing Superparamagnetic Nanocomposites

C. E. HOPPE; F. RIVADULLA; M. A. LÓPEZ-QUINTELA; M. C. BUJÁN; J. RIVAS; D. SERANTES; D. BALDOMIR

journal of physical chemistry C

American Chemical Society

Año: 2008 vol. 112 p. 13099 - 13104

1932-7447

Superparamagnetic polymer nanocomposites with well differenced distribution of the nanofiller in the matrix were obtained by using oleic-acid coated maghemite nanoparticles. Both homogeneously dispersed magnetic films and dispersions constituted by a distribution of submicrometric nanoparticles (NPs) clusters could be obtained starting from the same batch of magnetic NPs. We demonstrated that differences in the magnetic behavior of these materials are solely due to changes in the NPs spatial distribution not involving changes in their size or total volume fraction. The experimental behavior of random distributions of NPs was consistent with Monte Carlo (MC) simulations performed on equivalent systems. On the contrary, presence of aggregates produced higher values of the blocking temperatures (TB) due to the increase in the strength of dipolar interactions produced by the increase of local concentration in the aggregated domains. In this way, we determined that clustering, even in the submicrometric range, strongly controls the magnetic behavior of nanocomposites. This is of fundamental importance in the design of new magnetic materials with technological applications.