Spin-driven Electric Polarization in Asymmetric van der Waals Magnets

Magnetoelectric coupling is a fundamental physical issue, which enables electric-field control of magnetism for realizing next-generation high-performance spintronic devices. However, magnetoelectric coupling in two-dimensional (2D) van der Waals (vdW) interfaces is usually too weak for practical uses. Here we propose a general mechanism of spin-driven electric polarization, which indicates strong magnetoelectric couplings in 2D vdW systems for efficient electric-field switching of spin orders. The interlayer spin interaction in an asymmetric vdW magnet inherently generates an additional electric polarization, which is sensitive to the spin orders. This provides a spin degree-of-freedom in addition to lattice displacement and/or charge transfer for altering electric polarization. As a result, spin-parallel and -antiparallel orders could exhibit distinct electric polarizations, suggesting that the spin orders can be switched, in reverse, by manipulating the electric polarization through applying static electric fields. We validate this mechanism through a tight-binding double atomic chain model and comprehensive high-throughput first-principles calculations on over 800 2D asymmetric magnetic systems, including vdW heterobilayers, vdW homobilayers with substrates, MXenes, and polar slabs sandwiched by transition metals. This finding not only establish a fundamental and effective magnetoelectric coupling mechanism, but also provide a comprehensive dataset for realizing electric-field control of magnetism in 2D systems.