Magnetic field driven enhanced ferroelectric switching in self-grown ferroelectric-ferromagnetic composite in the BiFeO3-BaTiO3 multiferroic alloy system

摘要

Over the years attempts have been made to compensate for the inherentweaknesses in the bulk state of the multiferroic BiFeO3, such as high leakagecurrent and the absence of ferromagnetic correlation, and exploit itsmagnetoelectric potential by forming solid solutions with other perovskites.Studies in the recent few years have shown that alloying of BiFeO3 with BaTiO3,both with and without additives, can induce both ferroelectric andferromagnetic switching. While the coexistence of both the ferroic orders isencouraging from the view point of technological applications, the origin offerromagnetism in this system remains elusive. Here, we synthesized suchcompositions and carried out a detailed structural analysis employing magneticseparation of the powder particles. We found that the origin of ferromagnetismlies in the spontaneous precipitation of a minor ( ~ 1 wt %) barium hexaferrite(BaFe9O19) phase, often undetected in routine x-ray diffraction studies ofpowders sampled from the entire specimen. We also demonstrate that inspite ofthe insignificant fraction the ferrimagnetic phase, this self-grown compositeexhibit noticeably enhanced ferroelectric switching in the presence of externalmagnetic field. We obtained a dc magnetoelectric coupling of ~ 9 x 10-8 s/m, avalue which is comparable to what has been reported for layeredferroelectric/ferromagnetic laminates and bilayer thin filmferroelectric-ferromagnetic hetrostructures. Our study suggests that reasonablylarge magnetoelectric coupling is realizable in simple 0-3ferroelectric-ferromagnetic bulk composites provided synthesis strategies aredeveloped which induces spontaneous precipitation of the ferromagnetic phase insmall volume fraction to ensure good insulating behaviour of the composite thusdeveloped.