Tri-coordinated Au dopant induced out-of-plane ferroelectricity and enhanced ferromagnetism in chromium triiodide

Abstract

The coexistence of out-of-plane ferroelectricity and ferromagnetism in one single two-dimensional (2D) material is extremely rare but of great importance for both the fundamental understanding of low-dimensional condensed matter physics and the practical applications in next-generation electronic/spintronic devices. Herein, by first-principles calculations, we unveil that Au doping can simultaneously induce switchable electric polarization and enhance the intrinsic ferromagnetism of 2D chromium triiodide (CrI₃). The Au dopant occupies one side of the I₆ hollow site and displays a distorted trigonal planar coordination, which is stabilized by the enhanced Au-6s/I-5s and Au-6s/I-5p bonding interactions. Such tri-coordinated Au dopant destroys the lateral centrosymmetry of CrI₃, resulting in large out-of-plane electric dipoles that can be switched under a low transition barrier. Moreover, the super-exchange Cr–I–Cr interactions and magnetic anisotropic energy of 2D CrI₃ are all strengthened through Au doping. Our results demonstrate the possibility of engineering lateral ferroelectricity through elemental doping to 2D CrI₃ and the proposed ferroelectric magnet, Au-doped CrI₃, shows promising applications in nanosized electronic and spintronic devices.