Multiferroic Core-Shell Nanofibers, Assembly in a Magnetic Field, and Studies on Magneto-Electric Interactions

Abstract

Ferromagnetic–ferroelectric nanocomposites are of interest for realizing strong strain-mediated coupling between electric and magnetic subsystems due to a high surface area-to-volume ratio. This report is on the synthesis of nickel ferrite (NFO)–barium titanate (BTO) core–shell nanofibers, 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 in 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 ~2–7% 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.

Magnetoelectric coupling in CoFe2O4‐Pb(Zr0.2Ti0.8)O3 coaxial nanofibers

“…The force of attraction or repulsion between the CFO core and the magnetic tip induces a clear contrast in the middle area of the fiber. 26,27 The frequency response of MFM was used to investigate the electric-field-induced magnetization. The magnetic domains in coaxial NF were firstly scanned by using MFM mode.…”

“…MFM phase and frequency images in Figure 4C,D clearly show different contrasts in the CFO core and PZT shell area. The force of attraction or repulsion between the CFO core and the magnetic tip induces a clear contrast in the middle area of the fiber 26,27 . The frequency response of MFM was used to investigate the electric‐field‐induced magnetization.…”

A review on electrospun magnetic nanomaterials: methods, properties and applications

“…2(i)), Janus array fibre films 28,35,47 and oriented coaxial fibres. 48 Wang et al 36 fabricated highly fluorescent membranes made up of Janus NFs composed of magnetic [Fe 3 O 4 /polyvinylpyrrolidone (PVP)] and fluorescent terbium ligand complex Tb(BA) 3 phen/PVP (where BA is benzoic acid and phen is phenanthroline) NFs. The trifunctional bi-layered composite nanofibrous film was produced using layerby-layer electrospinning and by systematically altering the process parameters during the electrospinning process.…”

Most recent developments in electrospun magnetic nanofibers: A review

“…24 Nickel ferrite-barium titanate core-shell nanofibers were created by magnetic field-assisted electrospinning, allowing for assembling them into disks or films in a uniform or gradient magnetic field. 25…”