Time-dependent magnetization in co-precipitated cobalt ferrite

Abstract

A study of the magnetic aftereffect in co-precipitated cobalt ferrite is presented. Measurements of the magnetic viscosity S were performed at room temperature along the demagnetization curve for different applied fields H ap over a wide range of fields (0 kOe<H ap < - 7kOe). The interrelation function η=(∂M rev /∂M irr ) Hi between the DCD reversible M rev and irreversible M irr magnetization components was determined as well. The experimental results for S η (H i ), where H ι is the internal field, showed a broad distribution with a maximum at H ι = 2.7kOe. However, the irreversible susceptibility X irr displays a maximum at H c = 0.75 kOe, the coercivity of the material. The experimental behavior of η and the non-proportionality between S η and X ι ιrr suggest that the magnetic viscosity in this material is principally supplied by events of nucleation of inverse domains and the depinning of domain walls. When the main mechanism of reversal magnetization changes to rotation of magnetic moments for all the grains, the magnetic viscosity decreases.