CHARACTERIZATION OF A FERROGEL OF IRON OXIDE MAGNETIC NANOPARTICLES IN A PVA NETWORK

LORENA ARCINIEGAS; PEDRO MENDOZA ZÉLIS; GUSTAVO ALBERTO PASQUEVICH; JIMENA GONZÁLEZ; CRISTINA HOPPE; VERA ALVAREZ; FRANCISCO HOMERO SÁNCHEZ

Buenos Aires

Congreso; X LAW3M (Tenth Latin American Workshop on Magnetism, Magnetic Materials and their Applications); 2013

Asociación Física Argentina

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 14 K and 300 K at 825 Hz. Finally M vs H cycles were measured at dierent temperatures from 10 K to 290 K, and FC-ZFC magnetization was recorded in the same temperature range under 4 kA/m and 8 kA/m elds in a SQUID[3]. ZFC measurements showed an average temperature maximum of 17- 25 K. From analysis, we obtained a characteristic NP diameter D between 4.9 - 5.6 nm. 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 eect of dipolar interactions among particles[4]. TEM observations indicate a homogeneous distribution of NPs with a mean distance between them d 3D, therefore suggesting no important dipolar eects. The observed behavior of saturation magnetization Ms vs T gives an evidence of moment collective oscillations leading to Ms(T) = Ms(0)(1-aT)[5], where a= kb*B/KV, being kB the Boltzmann constant, K the NPs magnetic efective anisotropy constant, and V the NPs mean volume. Possible origins of the nonphysical NPs apparent moment temperature behavior will be discussed.