Creating half-metallicity in two-dimensional magnetoelectric materials

Abstract

Magnetic two-dimensional (2D) materials [1, 2] opened unprecedented opportunities for nanoscale spintronic devices in miniaturized form factor. With the aggressive pursuit for dimensional scaling is another paramount endeavor, persistently ongoing for high power efficiency [3]. Under this energy consumption umbrella, high spin polarization is one critical prerequisite. In this talk, I will introduce two schemes [4, 5] to create half-metallicity in layered material systems. In scheme I [4], electric field will be applied across the bilayer A-type antiferromagnetic 2D materials. By electrostatically changing the relative energy levels of the two spin-polarized bands in the two layers, one spin-polarized band from both layers will be merged whereas the other spin-polarized band will be opened with a gap, leading to half-metallicity (i.e., 100% spin polarized conductive electrons). In scheme II [5], a multiferroic superlattice consisting of alternative ferroelectrics and A-type antiferromagnets is constructed. In ferroelectric phase, the two interfaces on the opposite sides of the ferroelectric layer will be made half metallic, with 2D electron gas and 2D hole gas of the same pure spin polarization created at the alternative interfaces. With the opposite ferroelectric polarization, the half metallicity of the opposite spin polarization will be produced, leading to ferroelectric switching of the interfacial half metallicity. Both schemes are generic and experimentally practical, and will provide valuable contributions to the developments of miniaturized, high-efficiency spintronics.