Reversible-irreversible magnetization processes and remanence properties of coprecipitated cobalt ferrite.

Cobalt ferrite was obtained by coprecipitation of iron (II) sulphate and cobalt (II) sulphate in acetone medium. Using the moving Preisach model, the reversible (M(rev)) and irreversible (M(irr)) components of the magnetization were separated. The parameter eta given by eta = (dM(rev) / dM(irr))(Hi) and the moving Preisach parameter k(m), were evaluated according to the relation eta = k(m)chi (rev) in order to investigate the behavior of M(rev). It was found that eta is not proportional to the reversible susceptibility, therefore k(m) is a function of the internal field. Isothermal remanent magnetization (IRM) and DC demagnetization (DCD) curves were measured. From these data the deltam curve and the Henkel plot were obtained showing that all the points remain under the Wohlfath line indicating that the local disorder dominates (demagnetizing-like effect) over the mean-field effect. The switching field distribution curves were obtained by differentiation of the IRM and DCD curves. The peak values of these switching field distributions differ by a factor of 2.7.