Using FORC method in detection multiple magnetic components in magnetoelectric composites

Core-shell multiferroic nanocomposites formed by a magnetic core (-Fe2O3) and BaTiO3 ferroelectric shell were prepared and then densified either by classical sintering at various temperatures (10500C- 11500C) or by spark plasma sintering [1]. Besides the properties of the parent materials Fe2O3 and BaTiO3, variable amounts of secondary phases (Fe3O4, BaFe12O19 and Ba12Fe28Ti15O84) have driven to new functional properties in the ceramic composites. Dielectric and magnetic properties were determined and discussed in correlation with the sample microstructures, composition and degree of connectivity. Peculiar magnetic properties, including "wasp-waisted" constricted M(H) loops were determined as result of the formation of magnetic phases with contrasting magnetic coercivities (hard and soft phases) (Fig. 1 a, b). Since the M(H) response is dominated by the high-magnetisation components and in order to understand the magnetic properties induced by the secondary phases formation, first-order-reversal FORC method was employed, allowing to determine the Preisach-like distribution over coercivities and interaction fields (Fig. 1 c, d) [2]. This method allowed to detect magnetic components with contrasting coercivities formed at interfaces, in very small amounts below the XRD detection limits (e.g. the transformation of Fe2O3/Fe3O4 under reducing conditions).