Interparticle Magnetic Interactions in Grafted Maghemite Nanoparticles

MOSCOSO LONDOÑO, O; LEDE, E. J; COSIO CASTAÑEDA, C; RICARDO MARTÍNEZ GARCÍA; SOCOLOVSKY, L. M

Congreso; X LAW3M - Latin American Workshop on Magnetism; 2013

Interparticle interactions in maghemite ( -Fe2O3) nanoparticles are studied by DC magnetization measurements. Two batches of nanoparticles, one with median diameter of 3-nm and other with 9-nm, were prepared by chemical synthesis in order to study the eect of size on magnetic interactions. Their structural features were studied by High Resolution Transmission Electron Microscopy and X-Ray Absorption Spectroscopy. Maghemite compounds were obtained by a swift neutralization reaction of ferric solution (3-nm samples) and by a sol-gel self combustion process (9-nm samples). After samples were synthesized, these were coated and dispersed in dierent molar concentration of citric acid maintaining the relationship between citric acid volume and nanoparticle surface area in order to keep grafting homogeneous. 3-nm samples shows maghemite crystallites and very small quasi-crystals. 9-nm samples are composed by well formed maghemite nanoparticles. Dierent magnetic behaviors are observed for both systems for dierent concentrations: from a superparamagnetic state without interactions up to a superspin glass state. We will discuss the observed behaviour in the light of the dipolar magnetic interaction models.