Multiferroic Properties and Magnetic Anisotropy in P(VDF-TrFE) Composites with Oriented CoFe₂O₄Nanofibers

Multiferroic materials have good application prospect in the field of non-volatile random access memory due to the simultaneous existence of ferroelectricity, ferromagnetism, and the coupling between them. In this work, two kinds of nanofibers (pure CoFe2O4 nanofibers and CoFe2O4 nanofibers coated with a BaTiO3 layer) were designed and fabricated. P(VDF-TrFE)-based composites with aligned nanofibers were prepared via high-speed directional electrospinning. The effect of ferromagnetic nanofibers on the ferroelectricity of composites was investigated, and the multiferroic performance and magnetic anisotropy were observed. The leakage current of the composite can be well suppressed after coating the BaTiO3 layer, and it makes the composite possess enhanced ferroelectric and ferromagnetic properties at the same time. Notably, the maximum polarization and remnant polarization of a 10 vol % P(VDF-TrFE)/CoFe2O4@BaTiO3 composite reach 8.0 and 7.0 μC/cm2, respectively, when the applied electric field is 1000 kV/cm. Meanwhile, the maximum magnetization and remnant magnetization are 5.9 and 2.0 emu/g at 20,000 Oe, respectively, and the magnetization along the nanofiber direction is larger than that perpendicular to the nanofiber direction on the surface of the composites. The maximum values of the magnetoelectric voltage coefficient reached 5111 mV/cm·Oe (Hdc = 8083 Oe) for the 5 vol % P(VDF-TrFE)/CoFe2O4@BaTiO3 composite. The excellent ferroelectric and ferromagnetic properties in a high electric field make flexible composites promising to be an ideal material for improving the multiferroic devices.