Abstract
Atomically thin two-dimensional (2D) magnets have given rise to emergent phenomena due to magnetic exchange and spin-orbit coupling showing great promise for realizing ultrathin device structures. In this paper, we critically examine the magnetic properties of 2D ${\mathrm{FeS}}_{2}$, a non van der Waals magnet, 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 100 K 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 noncollinear 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.
Highlights
Magnetism in two dimensions (2D) has long been at the heart of numerous theoretical, experimental, and technological advances as thi research area has been proven to be a fertile ground for emergent magnetic phenomena, such as the study of topology [1,2,3], multiferroicity [4,5,6,7], proximity effects in heterostructures [8], etc
Our accurate calculations of total energies indicate that the FeS2 (111) surface with an AFM configuration has lower energy compared to the FM state, which is in contrast to some previous studies [27,29]
This magnetic coupling-dependent Fe-Fe distance indicates the presence of spin-lattice coupling. It means that the magnetic configuration is tunable by introducing external strain along a specific direction. It implies that the ferromagnetism observed in recent experiments might have been triggered by strain
Summary
Magnetism in two dimensions (2D) has long been at the heart of numerous theoretical, experimental, and technological advances as thi research area has been proven to be a fertile ground for emergent magnetic phenomena, such as the study of topology [1,2,3], multiferroicity [4,5,6,7], proximity effects in heterostructures [8], etc. Long-range magnetic order is prohibited in the 2D isotropic-Heisenberg model at a finite temperature by the Mermin-Wagner theorem. Symmetry breaking, such as the occurrence of magnetic anisotropy, removes this restriction. The challenge is to have a magnetic long-range order and thermal stability at room temperature and above
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