Extraordinary role of Ce-Ni elements on the electrical and magnetic properties of Sr-Ba M-type hexaferrites

The structural, electrical and magnetic behavior of Sr0.5Ba0.5-xCexFe12-yNiyO19 (where x = 0.00-0.10: y = 0.00-1.00) hexaferrite nanomaterials are reported in this paper. The structural analysis indicates that the Ce-Ni doped Sr-Ba M-type hexaferrite samples synthesized by the co-precipitation method are stoichiometric, single magnetoplumbite phase with crystallite sizes in the range of 35-48 nm. The dc-electrical resistivity of the pure Sr-Ba hexaferrite is enhanced to almost 10(2) times by doping with Ce-Ni contents of x = 0.06; y = 0.60. The dielectric constant and dielectric loss tangent decrease to values similar to 14 and <0.2, respectively, by increasing the frequency up to 1 MHz. Small relaxation peaks at frequencies > 10(5) Hz are observed for the samples with Ce content of x > 0.06. The values of saturation magnetization increase from 66.32 to 84.33 emu/g and remanance magnetization from 42.64 to 56.01 emu/g but coercivity decreases from 2.85 to 1.59 kOe by substitution of Ce-Ni. Sharp ferri-para magnetic transition is observed in the samples, which is confirmed by DSC results. Ce-Ni substitution acts to reduce the electron-hopping between Fe2+/F3+ ions and also improves the magnetic properties. These characteristics are desirable for their possible use in microwave and chip devices. (C) 2009 Elsevier Ltd. All rights reserved.