The role of cluster microstructure on the exchange coupling interaction between magnetically hard and soft phases

Abstract

Nanocomposites of Al-doped Barium Ferrites mixed with Nickel Ferrite were synthesized and characterized using various techniques. We investigated the role of cluster microstructure on the exchange coupling interaction between magnetically hard and soft phases in nanostructured composites consisting of Al-doped barium ferrites mixed with nickel ferrite. The magnetic response of the composites showed an “S-shaped” curve, but there were weak or no signs of magnetic exchange coupling, even though the nanoparticles of the two phases had a ratio within the range where this interaction would be possible. The presence of the mentioned clusters can explain the latter phenomenon. We quantified microstructural parameters and analyzed their correlation with magnetic behavior, focusing on two specific composites: one with minimal magnetic interaction (80% BaFe12O19 and 20% NiFe2O4) and another with no interaction (80% BaFe10.5Al1.5O19 and 20% NiFe2O4). In the mentioned samples a distribution of sizes of the clusters of NiFe2O4 were obtained by image analysis of the EDAX nickel mapping picture. Also Henkel plots were used to determine the quantity and distribution of dipolar magnetic interaction and exchange coupling magnetic interaction between the phases. The composites exhibited a disordered microstructure with clusters of NiFe2O4 dispersed in the BaFe12O19 matrix. Our results indicate that the size of the clusters is an important factor in determining the strength of the exchange coupling interaction. Our findings have implications for designing and optimizing magnetic materials with enhanced exchange coupling interaction.