Interaction effects on the coercivity and fluctuation field in granular powder magnetic systems

In this paper, the interaction effects on the coercivity (H c) and Fluctuation fields (H f) of doped barium-ferrite particles at different concentrations are examined. Samples with different concentrations are prepared by mixing the original powder with a non-magnetic host. Coercivity measurements at different particle concentrations showed that for high concentrations, the coercivity decreases with decreasing particle concentration. This attributed to the reduction of positive dipolar interactions that arise from stacking effects. However, at very low concentrations, H c is observed to increase with decreasing concentration due to the reduction in the predominant negative dipolar interactions. Measurements of fluctuation field using the waiting time technique show that the behavior of H f at different concentrations is greatly influenced by particle interactions. This result can be understood since H f is governed by the distribution of effective energy barriers F(ΔE eff)