Abstract
van der Waals (vdW) magnets have emerged as a tunable platform for exploring a variety of layer-dependent magnetic phenomena. Here we probe the thickness-dependent magnetism of vanadium triiodide (VI3), a material known as a layered ferromagnetic Mott insulator in its bulk form, using magnetic circular dichroism microscopy. Robust ferromagnetism is observed in all thin layers, down to the monolayer limit with large coercive fields. In contrast to known vdW magnets, the Curie temperature shows an anomalous increase as the layer number decreases, reaching a maximum of 60 K in monolayers. Second harmonic generation measurements reveal broken inversion symmetry in exfoliated flakes, down to trilayers. This observation demonstrates that the exfoliated flakes take a layer stacking arrangement that differed from the inversion-symmetric parent bulk counterpart. Our results suggest a coupling effect between magnetic and structural degrees of freedom in VI3 and its potential for engineering layer and twist angle-dependent magnetic phenomena.
Original language | English |
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Pages (from-to) | 9180-9186 |
Number of pages | 7 |
Journal | Nano Letters |
Volume | 21 |
Issue number | 21 |
DOIs | |
State | Published - Nov 10 2021 |
Funding
The authors acknowledge Shiwei Wu for the helpful discussion on second harmonic generation results and Werner Kaminsky for help with XRD characterization of bulk VI crystals. This work was solely supported as part of Programmable Quantum Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), under award no. DE-SC0019443. M.M.’s crystal synthesis effort at ORNL was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences, and Engineering Division. 3
Keywords
- 2d material
- Curie temperature
- Magnet
- Stacking