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

Cobalt ferrite was obtained by coprecipitation of iron (II) sulphate and co balt (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) a nd the moving Preisach parameter k(m), were evaluated according to the rela tion 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, th erefore k(m) is a function of the internal field. Isothermal remanent magne tization (IRM) and DC demagnetization (DCD) curves were measured. From thes e data the deltam curve and the Henkel plot were obtained showing that all the points remain under the Wohlfath line indicating that the local disorde r dominates (demagnetizing-like effect) over the mean-field effect. The swi tching field distribution curves were obtained by differentiation of the IR M and DCD curves. The peak values of these switching field distributions di ffer by a factor of 2.7.