Enhanced magnetoelectric coupling response in hot pressed BiFeO3 and polymer composite films: Effect of magnetic field on grain boundary and grain resistance

•Study on Cole-Cole plots indicates that the value of GBR is higher than GR.•∆GBR is found to be higher than ∆GR.•α33 (2.7 mV/cm-Oe) is found to be higher for the composite film of BFO50.•PFM study reveals that BFO50 composite film has a strong ME. We report the effect of grain boundary resistance (GBR) and grain resistance (GR) on the magnetoelectric coupling in the multiferroic composite thick films of BiFeO3 (BFO) nanocrystalline powder and poly vinylidene-fluoride (PVDF) polymer. These composite thick films of thickness ∼ 0.2 mm were prepared via hot pressing with the weight ratio of BFO powder and PVDF polymer as 70:30 (abbreviated as BFO70), 60:40 (abbreviated as BFO60), 50:50 (abbreviated as BFO50) and 40:60 (abbreviated as BFO40), respectively. Impendence investigations (Cole-Cole plots) of these thick films demonstrate that the GBR is significantly changed on the application of magnetic field (8 kOe) in comparison to the GR. Our results indicate that the GBR plays an important role in strengthening of magnetoelectric (ME) effect in BFO-PVDF system. In addition, the ME coupling study indicates that the BFO50 sample shows better results (α33 ∼ 2.7 mV/cm-Oe) and may be suitable for device and sensor applications. [Display omitted]