Multiferroic Core-Shell Nanofibers, Assembly in a Magnetic field and Studies on MagnetoElectric Interactions

TL;DR

This paper reports the synthesis, assembly, and magneto-electric interaction studies of nickel ferrite-barium titanate core-shell nanofibers, demonstrating strong coupling effects useful for advanced multifunctional materials.

Contribution

It introduces a novel synthesis and assembly method for core-shell nanofibers and models their magneto-electric interactions, advancing understanding of strain-mediated coupling in nanocomposites.

Findings

Measured 2-7% change in polarization and permittivity under magnetic field.

Observed a magneto-electric voltage coefficient of 0.4 mV/cm Oe at 30 Hz.

Developed a theoretical model for low-frequency magneto-electric effects.

Abstract

Ferromagnetic-ferroelectric nanocomposites are of interest for realizing strong strain mediated coupling between electric and magnetic subsystems due to high surface area-to-volume ratio. This report is on the synthesis of nickel ferrite (NFO) -barium titanate (BTO) core-shell nano-fibers, magnetic field assisted assembly into superstructures, and studies on magneto-electric (ME) interactions. Electrospinning techniques were used to prepare coaxial fibers of 0.5-1.5 micron in diameter. The core-shell structure of annealed fibers was confirmed by electron microscopy and scanning probe microscopy. The fibers were assembled into discs and films in a uniform magnetic field or a field gradient. Studies on ME coupling in the assembled films and discs were done by magnetic field H induced polarization, magneto-dielectric effects at low frequencies and at 16-24 GHz, and low frequency ME voltage coefficients (MEVC). We measured 2~ 2-7% change in remnant polarization and in the permittivity for H = 7 kOe, and a MEVC of 0.4 mV/cm Oe at 30 Hz. A model has been developed for low-frequency ME effects in an assembly of fibers and takes into account dipole-dipole interactions between the fibers and fiber discontinuity. Theoretical estimates for the low-frequency MEVC have been compared with the data. These results indicate strong ME coupling in superstructures of the core-shell fibers.