Magnetic switching of the ferroelectric polarization in a patterned medium mediated by magnetostriction and flexoelectricity

Multi-component metal/organic multilayers and hybrid nanostructures of 1-3 connected architecture exhibit room temperature tuning of the electrical polarization by a magnetic field but permanent domain reversal by a magnetic field is difficult. In our prior study with 1-3 connected multiferroic hybrid layer consisting of ferromagnetic nickel nanopillars regularly embedded in a ferroelectric co-polymer(PVDF:TrFE) matrix, polarization could be switched using magnetic field up to 0.5 T aided by a weak electric field. In this work, we fabricate the reverse geometry of ferroelectric polymer nanopillars embedded in a Ni matrix. On application of a vertical magnetic field, the Ni matrix with negative magnetostriction expands in the plane and compress out of the plane of the device which being physically clamped to the substrate results in a strain gradient along the ferroelectric nanopillars.The strain gradient in turn produces an equivalent electric field by the flexoelectric effect, which is of the same magnitude as the field required to switch a negatively poled ferroelectric domain of the copolymer. This was confirmed by piezoelectric force microscopy and finite element simulations, where switching reversal of a negatively poled domain was induced by the application of 0.7 T alone.