Strain-mediated magneto-electric effects in coaxial nanofibers of y/w-type hexagonal ferrites and ferroelectrics

Abstract

Nanofibers of Y-or W-type hexagonal ferrites and core–shell fibers of hexagonal ferrites and ferroelectric lead zirconate titanate (PZT) or barium titanate (BTO) were synthesized by elec-trospinning. The fibers were found to be free of impurity phases, and the core–shell structure was confirmed by electron and scanning probe microscopy. The values of magnetization of pure hexagonal ferrite fibers compared well with bulk ferrite values. The coaxial fibers showed good ferroelectric polarization, with a maximum value of 0.85 µC/cm2 and 2.44 µC/cm2 for fibers with BTO core–Co2 W shell and PZT core–Ni2 Y shell structures, respectively. The magnetization, however, was much smaller than that for bulk hexaferrites. Magneto-electric (ME) coupling strength was characterized by measuring the ME voltage coefficient (MEVC) for magnetic field-assembled films of coaxial fibers. Among the fibers with Y-type, films with Zn2 Y showed a higher MEVC than films with Ni2 Y, and fibers with Co2 W had a higher MEVC than that of those with Zn2 W. The highest MEVC of 20.3 mV/cm Oe was measured for Co2 W–PZT fibers. A very large ME response was measured in all of the films, even in the absence of an external magnetic bias field. The fibers studied here have the potential for use in magnetic sensors and high-frequency device applications.