Unraveling complex magnetism in two-dimensional FeS$_2$

TL;DR

This study investigates the magnetic properties of two-dimensional FeS$_2$, revealing an antiferromagnetic ground state with potential for strain-induced ferromagnetism and non-collinear structures, challenging previous claims of room temperature ferromagnetism.

Contribution

The paper provides the first ab initio analysis showing antiferromagnetic ground state and strain-tunable magnetic structures in 2D FeS$_2$, contrasting prior experimental claims.

Findings

Ground state is antiferromagnetic with ~100K ordering temperature.

Spin-phonon coupling may enable strain-induced ferromagnetism.

Potential for non-collinear magnetic structures under strain.

Abstract

Atomically thin two dimensional magnets have given rise to emergent phenomena due to magnetic exchange and spin-orbit coupling showing a great promise for realizing ultrathin device structures. In this paper, we critically examine the magnetic properties of 2D FeS$_2$, which has been recently claimed to exhibit room temperature ferromagnetism in the (111) orientation. Our ab initio study based on collinear density functional theory has revealed the ground state as an antiferromagnetic one with an ordering temperature of around 100K along with a signature of spin-phonon coupling, which may trigger a ferromagnetic coupling via strain. Moreover, our calculations based on spin-spirals indicate the possibility of non-collinear magnetic structures, which is also supported by Monte Carlo simulations based on ab initio magnetic exchange parameters. This opens up an excellent possibility to manipulate magnetic structures by the application of directional strain.