FeCo flower–like nanoparticles embedded in PVDF–HFP fibers as efficient magnetoelectric composite

Abstract

In this study, novel magnetoelectric (ME) composites consisting of flower-like FeCo nanoparticles embedded in PVDF-HFP fibers and films were fabricated via electrospinning and solution casting. Samples containing 0.1, 7, and 22 wt% FeCo were examined to elucidate how nanoparticle loading, morphology, and architecture affect structure, magnetic properties, ferroelectricity, and ME performance. The composites were characterized by TEM, SEM, XRD, FTIR, Mössbauer spectroscopy, SQUID magnetometry, ferroelectric testing, and ME coupling coefficient measurements. Electrospun PVDF-HFP fibers exhibited a strong structural α→β transformation, reaching high electroactive β-phase fractions, while cast films predominantly formed the γ-phase. The flower-like FeCo morphology increased surface-to-volume ratio and facilitated efficient strain transfer at the polymer–particle interface. Post–processing through cold and hot pressing enhanced the mechanical strength of the composites and improved interfacial phase bonding, leading to strong magnetoelectric coupling under low magnetic fields. Under AC magnetic excitation of 2–12.5 Oe at 30 kHz, all samples demonstrated ME voltage response. The highest ME coefficient, αME≈450mV/cmOe, was obtained for cold-pressed electrospun fibers with 0.1 wt% FeCo, correlating directly with high β-phase content (≈93.7 %) and uniform nanoparticle dispersion. A clear dependence of ME output on phase composition, particle distribution, and processing parameters was established. Comparison of 0–1 (fiber) and 0–3 (film) architectures using identical constituent materials revealed superior ME performance in the fiber-based composites. These findings highlight the potential of nanostructured PVDF-HFP/FeCo composites for low-field magnetoelectric sensing, energy-efficient multifunctional devices, and flexible electronics, while providing new quantitative insight into coupling mechanisms in soft-magnetic nanoparticle–polymer systems.