The impacts of molecular adsorption on antiferromagnetic MnPS3 monolayers: enhanced magnetic anisotropy and intralayer Dzyaloshinskii-Moriya interaction

In two-dimensional (2D) magnetic systems, significant magnetic anisotropy is required to protect magnetic ordering against thermal fluctuation. In this paper, we explored the effect of molecular adsorption on the magnetic anisotropy and intralayer Dzyaloshinskii-Moriya interaction (DMI) of monolayer MnPS3, combining the first-principles calculation and theoretical analysis. We find that molecular adsorption can break the spatial inversion symmetry in a 2D magnet, and results in a significant DMI, which is rare in pristine 2D magnets. For example, in an MPS-NO system, the magnitude of the asymmetric DMI vector increases 9 times, and the magnetocrystalline anisotropy increases 600 times compared with the pristine MPS monolayer. It is found the DMI mainly comes from the structural deformation after adsorption, whereas the increase of magnetocrystalline anisotropy mainly originates from a new 'bridge' super-exchange interaction between Mn ions and NO gas molecules. The calculated Mn-NO-Mn 'bridge' super-exchange coupling strength is much higher than the Mn-S-Mn coupling strength. Our findings offer a new strategy to increase the magnetic anisotropy and induce chiral magnetic structures in 2D magnets.

Automated summary

In this study, we investigated the effect of molecular adsorption on the magnetic anisotropy and intralayer Dzyaloshinskii-Moriya interaction (DMI) of monolayer MnPS3. We found that molecular adsorption can enhance the magnetic anisotropy and induce significant DMI in 2D magnets. The enhancement of magnetic anisotropy mainly originates from structural deformation, while the presence of a new 'bridge' super-exchange interaction between Mn ions and adsorbed molecules contributes to the increased DMI.