ESR studies on superparamagnetic Fe3O4 nanoparticles

Abstract

In this study we have investigated temperature and frequency dependence of magnetic properties of superparamagnetic iron oxide nanoparticles (SPION). ESR measurements have been carried out in a temperature range of 10-300 K. A single, relatively broad and temperature dependent EPR signal was observed at all measurement temperatures. The linewidth slightly increases with decreasing temperature down to 100 K, then it sharply increases down to 60 K. Below 60 K the trend is reversed and the linewidth start to decrease. The resonance field remains almost constant down to 100 K and decreases sharply as the temperature is decreased further. The resonance field of the ESR spectra of Fe <inf>3</inf>O<inf>4</inf> shows a linear dependence on microwave frequency. By using experimental results, the effective g-value and internal field are deduced as 1.9846 and -40 G, respectively. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. © 2008 Elsevier B.V., All rights reserved.