Two-dimensional spin-spiral materials with spins rotating on an inclined plane: PtCl2, PdCl2 and PdBr2

Interest in spin-spiral materials has been on the rise due to inherent magnetoelectric coupling with potential applications in spintronic devices. Two-dimensional PtCl2, PdCl2 and PdBr2 in the 1T phase have been theoretically predicted to be antiferromagnetic semiconductors [1]. However, there are no experimental investigations on these three materials yet. Here, by performing density-functional-theory calculations, we revisit these materials, considering non-collinear magnetic order. It is found that spin spirals are the lowest-energy magnetic ordering for all three materials in the 1T phase at the LDA+U level. Spins rotate in an inclined plane, which is quasi-parallel to the metal-halogen bond direction. The spin-spiral ground state and an indirect bandgap are robust for different U values. The spin-spiral induced polarizations of all three materials are comparable with that of monolayer FeOCl, which was predicted recently [2]. These results enrich the two-dimensional families of spin-spiral systems.

[1] Xinru Li et al., Nanoscale Adv. 2020, 2, 495–501
[2] De-liang Bao et al., Nano Lett. 2022, 22, 3598