Characterization of a ferrogel of iron oxide magnetic nanoparticles in a PVA network

L. ARCINIEGAS, P. MENDOZA ZÉLIS, G.A. PASQUEVICH, AND F.H. SÁNCHEZ; J. GONZÁLEZ, C. HOPPE, V. ALVAREZ,

Buenos Aires

Workshop; VII Latin American Workshop on Magnetism, Magnetic Materials and their applications; 2013

UBA-CNEA

Ferrogels (FGs) are nanocompounds made of magnetic nanoparticles (NPs) dispersed in a polymeric network (hydrogel). They found applications in artificial muscles and magnetically modulated drug administration. In this communication a study of the magnetic properties of polyvinyl alcohol (PVA)/iron oxide nanoparticles ferrogels synthetized by freezing-thawing method, is presented 1,2 M vs H cycles were recorded at RT in a VSM. Susceptometry studies were done between 14K and 300K at 825Hz. Finally M vs H cycles were measured at different temperatures from 10K to 290K, and FC-ZFC magnetization was recorded in the same temperature range under 4kA/m and 8kA/m fields in a SQUID4. ZFC measurements showed an average temperature maximum of 17-25K. From analysis, we obtained a characteristic NP diameter D between 4.9?5.6nm. The analysis of M vs H curves at all temperatures presents a systematic inconsistency: the NP moment seems to increase linearly with temperature. This type of behavior was attributed to an effect of dipolar interactions among particles3. TEM observations indicate a homogeneous distribution of NPs with a mean distance between them d ≥3D, therefore suggesting no important dipolar effects. The observed behavior of saturation magnetization Ms vs T gives an evidence of moment collective oscillations leading to Ms(T)= Ms(0)(1− αT)5, where α = kB/KV , being kB the Boltzmann constant, K the NPs magnetic effective anisotropy constant, and V the NPs mean volume. Possible origins of the non physical NPs apparent moment temperature behavior will be discussed. 1. Hassan CM, Peppas NA. Adv Polym Sci. (2000)153:37−65. 2. Gonzalez JS, Hoppe CE, Muraca D, Sánchez FH and Alvarez AV. Coll Polym Sci (2011) 289:1839?1846 3. P. Allia, et al. Phys. Rev. B (2001) 64:144420−144430 4. Red Nacional de Magnetismo y Materiales Magneticos. 5. S. Mørup, et al. 2010, 1, 48−54