AVS 47th International Symposium
    Magnetic Interfaces and Nanostructures Friday Sessions
       Session MI-FrM

Paper MI-FrM5
Preparation and Characterization of High-Coercivity Cobalt Ferrite Particles Using Microemulsions

Friday, October 6, 2000, 9:40 am, Room 206

Session: Magnetic Recording: Media and Heads
Presenter: H. Du, National University of Singapore
Authors: H. Du, National University of Singapore
Y. Kim, National University of Singapore
S.L. Lim, National University of Singapore
L. Si, National University of Singapore
J. Ding, National University of Singapore
W.S. Chin, National University of Singapore
Correspondent: Click to Email
Ferrite materials in nano-scale are potential candidate for application on magnetic recording in high density and the study of nanoscale magnetic domains is of both fundamental and technical interest. In order to get uniform particles in nanosize, we attempted to separate the nucleation and growth processes. The nuclei of precursor hydroxides were formed in reverse micelles of sodium dioctyl sulfosuccinate (AOT). After separation from the microemulsion, the nanoparticles of about 10nm were calcined and the growth process was monitored. Transmission Electron Microscopy (TEM) results show that the irregular precursor nuclei will tend to form cubic shape and the particles grow larger to 20-30nm when the calcinations temperature is increased to 600°C. Lower temperature and longer calcination duration were favorable for the formation of monodispersed smaller particles. X-ray Diffraction (XRD) confirmed the crystalline nature of the ferrite particles. The compositions of the products was found to be determined by both the feed ratio of metal salts and the pH values of the microemulsion, which were analyzed through X-ray Photoelectron Spectroscopy (XPS) and Elemental Analysis. The magnetic properties of the nano-ferrites were measured using a Superconducting Vibration Sample Magnetometer (VSM). The cobalt ferrites nanoparticles synthesized had a relatively high coercivity (1555 Oe) and a saturation magnetization (77.32emu/g). The relationship between the magnetic properties and the crystal structure as well as the domain size will be discussed.