Magnetoresistive properties of Zn1-xCoxFe2O4 ferrites

The magnetic and magnetoresistive properties of spinel-type Zn1-xCoxFe2O4 (x = 0,0.2 and 0.4) ferrites are extensively investigated in this study. A large negative magnetoresistance (MR) effect is observed in Zn1-xCoxFe2O4 ferrites of spinel structure. These materials are either ferrimagnetic or paramagnetic at room temperature, and show a spin-(cluster) glass transition at low temperatures, depending on the chemical compositions. The MR curves as a function of magnetic fields, MR(H), are parabolic at all temperatures for paramagnetic polycrystalline ZnFe2O4. The MR for ZnFe2O4 at 110K in the presence of 9T applied magnetic field is 30%. On the other hand, MR(H) are linear for x = 0.2 and 0.4 ferrimagnetic Zn1-xCoxFe2O4 samples up to 9T. The MR effect is independent of the sintering temperatures, and can be explained with the help of the spin- dependent scattering and the Yafet-Kittel angle of Zn1-xCoxFe2O4 mixed ferrites. (C) 2007 Elsevier B.V. All rights reserved.