Magnetic ground state and strain-mediated chiral-like atomic distortion behavior in a two-dimensional rectangular spin lattice

Due to the large perpendicular magnetic anisotropy originating from spin-orbit coupling, magnetoelastic coupling is generally reported in easy-plane magnets with rectangular lattice where the easy axis is coupled with the lattice direction. Nevertheless, the acquisition of a coupling beyond the easy-plane ferromagnets in two-dimensional (2D) materials remains unknown. Here, by employing density functional theory calculations, we demonstrate this feasibility with the discovery of long-range ferromagnetic (FM) ordering and elastic strain-mediated chiral-like atomic distortion behavior in a newly tetragonal As-Fe-As trilayer (t-FeAs monolayer), which shows large perpendicular magnetic anisotropy, robust FM ordering, and in-plane ferroelasticity (FEL). We firstly point out that obvious limits exist when using the four magnetic configurations to determine the magnetic transition temperature for a rectangular spin lattice even if more exchange interaction parameters are included. A four-state mapping analysis is carefully examined for t-FeAs, where the calculated Curie temperature Tc is 435 K, which is higher than most reported 2D magnets and can be further tuned by appropriate strains. Intriguingly, the chiral-like atomic distortion behavior of the Fe sublayer is scanning-tunneling-microscopy characterizable, which can switch the magnetization axis between the out-of-plane and in-plane directions. This unusual finding of FEL manipulation of both the atomic displacement and spin properties makes t-FeAs a promising candidate for future spintronics and provides the possibility for exploring unprecedented coupling physics.