The effect of magnetic dilution of the magnetization reversal of coprecipitated barium ferrite powder

In a recent paper we reported upon first investigations on the hysteresis properties of magnetically diluted barium ferrite powder [1]. Using an improved method for the preparation of such samples, a strong dependence of the coercivity and the major hysteresis loop of the microwave absorption on the volumetric packing density p was demonstrated. Now we present the results of some more detailed investigations on the effect of dilution on the magnetic properties of isotropic powder samples of coprecipitated barium ferrite. First it will be proved that the strength of magnetic interaction within the samples is indeed influenced by the preparation method. This can be shown by comparing various remanence curves of the samples, as was first introduced by Wohlfarth [2]. A deeper insight into the magnetization processes then is obtained from the structure of the minor hysteresis loops of the microwave absorption. Because of the dependence of the resonance frequency on the equilibrium position of the magnetization vector these absorption curves are very sensitive to the magnetization reversal due to coherent rotation. They also include detailed informations about the reduced critical field strength akof the individual particle as a function of the orientation angle\varphi_{0}between the applied magnetic field and the easy axis of magnetization.