Moiré-Induced Magnetoelectricity in Twisted Bilayer NiI2
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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866909701181014016 |
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| author | Zhu, Haiyan Yu, Hongyu Zhu, Weiqin Yu, Guoliang Xu, Changsong Xiang, Hongjun |
| author_facet | Zhu, Haiyan Yu, Hongyu Zhu, Weiqin Yu, Guoliang Xu, Changsong Xiang, Hongjun |
| contents | Twisted magnetic van der Waals (vdW) materials offer a promising route for multiferroic engineering, yet modeling large-scale moiré superlattices remains challenging. Leveraging a newly developed SpinGNN++ framework that effectively handles spin-lattice coupled systems, we develop a comprehensive interatomic machine learning (ML) potential and apply it to twisted bilayer NiI2 (TBN). Structural relaxation introduces moiré-periodic "bumps" that modulate the interlayer spacing by about 0.55~Å and in-plane ionic shifts up to 0.48~Å. Concurrently, our ML potential, which faithfully captures all key spin interactions, produces reliable magnetic configurations; combined with the generalized KNB mechanism, it yields accurate spin-driven polarization. For twist angles 1.89^{\circ} \leq θ\leq 2.45^{\circ}, both mechanisms become prominent, yielding rich polarization textures that combine ionic out-of-plane dipoles with purely electronic in-plane domains. In the rigid (unrelaxed) bilayer, skyrmions are absent; lattice relaxation is essential for generating polar-magnetic topologies. In contrast, near θ \approx 60^{\circ}, stacking-dependent ferroelectric displacements dominate, giving rise to polar meron-antimeron networks. These results reveal cooperative ionic and spin-driven ferroelectricity in TBN, positioning twisted vdW magnets as adaptable platforms for tunable multiferroic devices. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_13709 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Moiré-Induced Magnetoelectricity in Twisted Bilayer NiI2 Zhu, Haiyan Yu, Hongyu Zhu, Weiqin Yu, Guoliang Xu, Changsong Xiang, Hongjun Materials Science Twisted magnetic van der Waals (vdW) materials offer a promising route for multiferroic engineering, yet modeling large-scale moiré superlattices remains challenging. Leveraging a newly developed SpinGNN++ framework that effectively handles spin-lattice coupled systems, we develop a comprehensive interatomic machine learning (ML) potential and apply it to twisted bilayer NiI2 (TBN). Structural relaxation introduces moiré-periodic "bumps" that modulate the interlayer spacing by about 0.55~Å and in-plane ionic shifts up to 0.48~Å. Concurrently, our ML potential, which faithfully captures all key spin interactions, produces reliable magnetic configurations; combined with the generalized KNB mechanism, it yields accurate spin-driven polarization. For twist angles 1.89^{\circ} \leq θ\leq 2.45^{\circ}, both mechanisms become prominent, yielding rich polarization textures that combine ionic out-of-plane dipoles with purely electronic in-plane domains. In the rigid (unrelaxed) bilayer, skyrmions are absent; lattice relaxation is essential for generating polar-magnetic topologies. In contrast, near θ \approx 60^{\circ}, stacking-dependent ferroelectric displacements dominate, giving rise to polar meron-antimeron networks. These results reveal cooperative ionic and spin-driven ferroelectricity in TBN, positioning twisted vdW magnets as adaptable platforms for tunable multiferroic devices. |
| title | Moiré-Induced Magnetoelectricity in Twisted Bilayer NiI2 |
| topic | Materials Science |
| url | https://arxiv.org/abs/2507.13709 |