Observation of grain size effect on multiferroism and magnetoelectric coupling of Na0.5Bi0.5TiO3 – BaFe12O19 novel composite system

Abstract

Four novel polycrystalline magnetoelectric composite systems: S1, S2, S3 and S4 having composition [90wt% Na0.5Bi0.5TiO3 (NBT) – 10wt% BaFe12O19 (BaM)] considering the variation of grain size of both the phases [NBT(Lg)-BaM(Lg)-[S1], NBT(Lg)-BaM(Sg)-[S2], NBT(Sg)-BaM(Lg)-[S3] and NBT(Sg)-BaM(Sg)-[S4]] are successfully synthesized by using solid state reaction method. Here, Lg is larger and Sg is smaller grain size respectively. The pure phase formation of desired composite systems is verified by Rietveld refinement of X-ray diffraction pattern. The Field Emission Scanning Electron Micrograph (FESEM) and Transmission Electron Micrograph (TEM) provided the information about the variation of grain size of both the phases. Room temperature ferromagnetic and ferroelectric properties have been estimated by VSM & PE loop tracer. Magnetoelectric coupling coefficient (αME) measurements has been performed by in-house ME setup. From the multiferroic and magnetoelectric data, it is surprisingly found that the composite system having a smaller grain size of NBT matrix and larger grain size of BaM disperse shows highest magnetoelectric coupling (αME) and remnant polarization (Pr) than others. It is also very interesting to observe that the drastic increase (more than 60%) of remnant magnetization (Mr) for composite systems which have smaller grain size of NBT matrix phase.