Anomalous behaviour of the magnetic hysteresis loop in the alpha-Fe2O3/SiO2 nanocomposite

Abstract

The alpha-Fe2O3/SiO2 nanocomposite containing 45 wt.% of hematite was prepared by the sol-gel method and characterized by using X-ray diffractometer (XRD), transmission electron microscopy (TEM) and. superconducting quantum interference device (SQUID) magnetometer. TEM microscopy showed spherical particles with average size about 10 nm, whereas XRD diffraction confirmed the formation of the hematite phase. The magnetic measurements showed anomalous behavior of the hysteresis loops including decrease of high field isothermal magnetization and overlap of initial, remagnetization and magnetization curves. This anomalous behavior represents a novel effect for alpha-Fe2O3/SiO2 nanocomposites. We conjecture that a field-induced antiferromagnetic coupling between nanoparticles may produce this effect. (C) 2009 Elsevier B.V. All rights reserved.