La_2NiMnO_6/poly(vinylidene fluoride) nanocomposites with enhanced magnetoelectric voltage

摘要

Multiferroic polymer composites of La_2NiMnO_6 and poly(vinylidene fluoride) (PVDF) in the form of disks and thick films were made via a two-step method and a solution casting method, respectively. These composite samples are studied via powder x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM). The XRD data revealed the biphasic (P2_1 + R-3c) crystal symmetry of La_2NiMnO_6 nanoparticles in the disk samples but monophasic (R-3c) crystal symmetry in the film sample. The formation of an electroactive P-phase of PVDF is observed in the FTIR spectra of a composite film sample. Estimation (via FTIR data) revealed the maximum p-phase fraction of PVDF (～37%) and zero porosity (in FESEM images) for the film sample. The magnetoelectric (ME) voltage measurement on these composite samples show significant ME voltage for temperatures as high as 400 K, which otherwise is zero for T ＞ 277 K in La_2NiMnO_6. Among the three composites, the film sample exhibited the maximum value of a first-order ME coefficient of 9.6 mV/cm Oe, and this value is at least two orders higher than that of the La_2NiMnO_6 pellet. Such a high value of ME coefficient favors this sample for its utilization in device applications and thus makes it technologically viable for ME based applications.