Flexoelectricity in Antiferromagnetic Nickel Oxide

Flexoelectricity describes the coupling between electric polarization and strain gradient. Because it is represented by a rank 4 tensor, it is not prohibited by the presence of inversion symmetry in a crystal in the same way as piezoelectricity. Despite being a ubiquitous phenomenon among dielectric materials, the set of materials whose flexoelectric effects have been studied is sparse. Here, we present a first-principles study on the flexoelectric coupling of antiferromagnetic NiO. We employ density functional perturbation theory to probe its bulk flexoelectric effect and utilize a recently developed technique to examine the mean-inner-potential contribution to flexoelectricity [1]. We report on magnetic contributions to the flexoelectric response in NiO and the possibility of a spin-polarized flexoelectric tensor. In addition to the applications of NiO in flexoelectric nanogenerators, we describe the relevance of flexoelectricity to corrosion of Ni-based alloys.

[1]        C. A. Mizzi and L. D. Marks, J. Appl. Phys. 129, 224102 (2021).