Factors influencing the remanent properties of hard magnetic barium ferrites: Impurity phases and grain sizes

In the present study, the effects of impurity phases and grain dimensions on the remanence properties of barium ferrite magnets are examined. The relationship between isothermal remanence MR (H) and demagnetization remanence MD (H) for non-interacting single domain particles, MD (H) =MR (Hmax)−2MR (H), was used in order to investigate the interactions between particles in barium ferrite samples. We have found that antiferromagnetic impurity phases (BaFe2O4 and Ba5Fe2O8) interact with the hard magnetic phase (BaFe12O19) and this interaction was observed to assist the persistence of the present magnetized state of the samples. Demagnetizing-like interactions occur between particles in case grain sizes are larger than single-domain limit (1 μm).