Phys. Rev. B 109, 195422 (2024)
Nanshu Liu, Cong Wang, Changlin Yan, Changsong Xu, Jun Hu, Yanning Zhang, and Wei Ji
Abstract:
A recent experiment reported type-II multiferroicity in monolayer (ML) NiI2 based on a presumed spiral magnetic configuration (Spiral-B), which is, as we found here, under debate in the ML limit. Freestanding ML NiI2 breaks its C3 symmetry, as it prefers a striped antiferromagnetic order (AABB-AFM) along with an intralayer antiferroelectric (AFE) order. However, substrate confinement may preserve the C3 symmetry and/or apply tensile strain to the ML. This leads to another spiral magnetic order (SpiralIVX), while 2L shows a different order (SpiralVX) and Spiral-B dominates in thicker layers. Thus, three multiferroic phases, namely, SpiralB+FE, Spiral-IVX +FE, Spiral-VX+FE, and an anti-multiferroic AABB-AFM+AFE one, show layer-thickness-dependent and geometry-dependent dominance, ascribed to competitions among thickness-dependent Kitaev, biquadratic, and Heisenberg spin–exchange interactions and single-ion magnetic anisotropy. Our theoretical results clarify the debate on the multiferroicity of ML NiI2 and shed light on the role of layer-stacking-induced changes in noncollinear spin–exchange interactions and magnetic anisotropy in thickness-dependent magnetism.
DOI: 10.1103/PhysRevB.109.195422 arXiv: 2211.14423 (2024)
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