Flexoelectric polarizing and control of a ferromagnetic metal

Abstract

Electric polarization is well defined only in insulators not metals, and there is no general scheme to induce and control bulk polarity in metals. Here we circumvent this limitation by utilizing a pseudo-electric field generated by inhomogeneous lattice strain, namely a flexoelectric field, as a means of polarizing and controlling a metal. Using heteroepitaxy and atomic-scale imaging, we show that flexoelectric fields polarize the bulk of an otherwise centrosymmetric metal SrRuO3, with off-centre displacements of Ru ions. This further impacts the electronic bands and lattice anisotropy of the flexo-polar SrRuO3, potentially leading to an enhancement of electron correlation, ferromagnetism and its anisotropy. Beyond conventional electric fields, flexoelectric fields may be used to create and control electronic states through pure atomic displacements.

Electric polarization is well defined for insulators but not for metals. Electric-like polarization is now realized via inhomogeneous lattice strain in metallic SrRuO3, generating a pseudo-electric field. This field affects the material's electronic bands.