Self-Biased Electrospun Triaxial Ferrite-PZT Nanofibers and Studies on Magneto-Electric Coupling

This work is on magneto-electric (ME) interactions in multiferroic composites of electro-spun triaxial nanofibers composed of lead zirconate titanate (PZT), strontium ferrite, SrFe12O19, (SrM), and nickel ferrite NiFe2O4 (NFO). M-type hexagonal ferrite, SrM, with a high uniaxial magneto-crystalline anisotropy field, was chosen to achieve a self-magnetic bias, and NFO with high magnetostriction and piezomagnetic coefficient was chosen to strengthen the ME coupling in the composites. By integrating these three distinct ferroic phases, the triaxial design optimizes interfacial strain transfer to enhance the ME coupling strength in the absence of an external magnetic bias. Fibers with PZT core (Sample A), SrM core (Sample B), or NFO core (Sample C) were synthesized and annealed at 750 C for crystallization of the ferroic phases. X-ray diffraction and electron and scanning probe microscopy confirmed the production of continuous, defect-free fibers with well-defined boundaries and coexisting crystalline phases free of impurities. Magnetic, ferroelectric, and magnetostrictive characterization verified ferroic ordering across all samples. Measurements of the ME voltage coefficients (MEVC) were carried out at low frequencies and at electromechanical resonance (EMR) on rectangular platelets of the fibers. A strong zero-bias ME response was measured, indicating an efficient strain-mediated coupling that bypasses the need for magnetic bias fields. Sample-C with NFO core, PZT inner shell, and SrM outer shell showed the highest low-frequency MEVC of 26.7 mV/cm Oe, and that increased to 161 mV/cm Oe at EMR, both values at zero bias. The stacking order of the core and shell phases dictated the resulting ME interactions. The results indicate the potential of these triaxial fibers as candidates for miniature magnetic sensors and arrays, multifunctional devices, and energy harvesters.