Structure and magnetic properties of nanocrystalline CoLa0.08Fe1.92O4 ferrite

The magnetic properties of nanocrystalline CoLa0.08Fe1.92O4 powders prepared by the emulsion method at room temperature have been studied by vibrating sample magnetometer (VSM). The structure and specific surface area were studied by X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET). The particle size of the powders varied from 13.3 to 264.2 nm by changing the calcinations temperatures and the corresponding specific saturation magnetization (a,) ranged from 48.8 to 78.4 emu/g. On increasing the particle size. the coercivity (H-c) first increased, passed through a maximum and then dropped. At room temperature, the nanocrystalline CoLa0.08Fe1.92O4 powders with a crystallite size of 63.6 nm achieved a desirable value of H-c = 1.51 kOe. A non-magnetic layer with the thickness of 1.1 nm exists at the surface of the particles. (c) 2005 Elsevier B.V. All rights reserved.