Magnetic properties of Ba-M-type hexagonal ferrites prepared by the sol-gel method with and without polyethylene glycol added

Ba-M-type hexagonal ferrites have been prepared via a sol-gel route, and the effects of adding different amounts of polyethylene glycol (PEG 2000) into the sol solutions on their static magnetic properties and particle morphologies also have been studied. With increasing the amount of PEG added, it is found that both the saturation magnetization and the coercivity decreases. The magnetocrystalline anisotropy constants have been obtained by fitting the magnetizing curves with the law of approach to saturation. The fitting results reveal that the magnetic anisotropy constants of ferrites with PEG added are smaller than that of the ferrites without PEG added. In addition, before the precursors were sintered at 800 degrees C, the phases of precursors obtained by the self-propagating combustions are found not the same for both ferrites prepared without and with PEG added. The results show that adding PEG into the sol solution is a good approach to tune the intrinsic coercivity. (C) 2008 Elsevier B.V. All rights reserved.