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

TL;DR

This study uses density functional theory to discover a 2D tetragonal As-Fe-As monolayer with high Curie temperature, perpendicular magnetic anisotropy, and strain-tunable chiral-like atomic distortions, revealing novel magnetoelastic coupling.

Contribution

It demonstrates the existence of long-range ferromagnetic order and strain-mediated chiral-like distortions in a new 2D tetragonal monolayer, expanding understanding of magnetoelastic effects beyond easy-plane magnets.

Findings

Curie temperature of 435 K, higher than most 2D magnets

Strain can tune magnetic properties and atomic distortions

Chiral-like atomic distortions can switch magnetization direction

Abstract

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 magnetization is coupled with the lattice direction, while the acquisition of a novel coupling, beyond the easy-plane ferromagnets, in two-dimensional (2D) materials remains unknown. Here, by employing the density functional theory calculations, we demonstrate this feasibility with the discovery of long-range ferromagnetic ordering and elastic strain-mediated chiral-like atomic distortions behavior in a newly tetragonal As-Fe-As trilayer (t-FeAs monolayer), which shows large perpendicular magnetic anisotropy, robust ferromagnetic ordering, and in-plane ferroelasticity. We firstly point out that obvious limits exist when using the four magnetic configurations to determine the magnetic ground state 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 sub-layer is scanning tunneling microscopy characterizable, which can switch the magnetization axis between the out-of-plane and in-plane direction. This unusual finding of ferroelastic manipulation of both the atomic displacement and spin properties makes t-FeAs a promising candidate for future spintronics and also provides the possibility for exploring unprecedented coupling physics.