Hierarchically nanostructured Fe3O4 microspheres and their novel microwave electromagnetic properties

Magnetite nanoparticles are found to assemble into monodisperse Fe3O4 microspheres with diameters similar to 300 nm and open pores on the shells in ethylene glycol (EG) in the presence of polyethylene 2000 (PEG 2000) and a small quantity of polyethyleneimine (PEI). The hysteresis loops of the magnetic microspheres are measured by a vibrating sample magnetometer (VSM), the ferromagnetic signature emerged with the saturated magnetization of similar to 80.0 emu g(-1), and the coercive force of similar to 208.7 Oe. The synthesized hierarchical microspheres exhibit two microwave magnetic loss peaks: one appears at 4.0-5.0 GHz, the other appears around 16.0-17.0 GHz. The latter peak is attributed to the effect of the morphology of the hierarchical structure. Modern analysis methods SEM, TEM, XRD etc., are employed to figure the detailed structure information of the magnetic hollow spheres Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.