Strain‐Modulated Ferromagnetism at an Intrinsic van der Waals Heterojunction

Strain‐Modulated Ferromagnetism at an Intrinsic van der Waals Heterojunction

Advanced Functional Materials

10.1002/adfm.202400552

http://dx.doi.org/10.1002/adfm.202400552

Ryuji Fujita, Gautam Gurung, Mohamad‐Assaad Mawass, Alevtina Smekhova, Florian Kronast, Alexander Kang‐Jun Toh, Anjan Soumyanarayanan, Pin Ho, Angadjit Singh, Emily Heppell, Dirk Backes, Francesco Maccherozzi, Kenji Watanabe, Takashi Taniguchi, Daniel A. Mayoh, Geetha Balakrishnan, Gerrit van der Laan, Thorsten Hesjedal

14 March 2024

Fujita, R., Gurung, G., Mawass, M., Smekhova, A., Kronast, F., Toh, A. K., Soumyanarayanan, A., Ho, P., Singh, A., Heppell, E., Backes, D., Maccherozzi, F., Watanabe, K., Taniguchi, T., Mayoh, D. A., Balakrishnan, G., van der Laan, G., Hesjedal, T. (2024). Strain‐Modulated Ferromagnetism at an Intrinsic van der Waals Heterojunction. Advanced Functional Materials. Portico. https://doi.org/10.1002/adfm.202400552

The van der Waals interaction enables atomically thin layers of exfoliated 2D materials to be interfaced in heterostructures with relaxed epitaxy conditions, however, the ability to exfoliate and freely stack layers without any strain or structural modification is by no means ubiquitous. In this work, the piezoelectricity of the exfoliated van der Waals piezoelectric α‐In2Se3 is utilized to modify the magnetic properties of exfoliated Fe3GeTe2, a van der Waals ferromagnet, resulting in increased domain wall density, reductions in the transition temperature ranging from 5 to 20 K, and an increase in the magnetic coercivity. Structural modifications at the atomic level are corroborated by a comparison to a graphite/α‐In2Se3 heterostructure, for which a decrease in the Tuinstra‐Koenig ratio is found. Magnetostrictive ferromagnetic domains are also observed, which may contribute to the enhanced magnetic coercivity. Density functional theory calculations and atomistic spin dynamic simulations show that the Fe3GeTe2 layer is compressively strained by 0.4%, reducing the exchange stiffness and magnetic anisotropy. The incorporation of α‐In2Se3 may be a general strategy to electrostatically strain interfaces within the paradigm of hexagonal boron nitride‐encapsulated heterostructures, for which the atomic flatness is both an intrinsic property and paramount requirement for 2D van der Waals heterojunctions.

Attribution 4.0 International (CC BY 4.0)

This research / project is supported by the A*STAR - Singapore's RIE2020 initiatives - AlScN Ferroelectrics program
Grant Reference no. : A20G9b0135

This research / project is supported by the A*STAR - Singapore's RIE2020 initiatives - SpOT-LITE program
Grant Reference no. : A18A6b0057

This project is supported by the Oxford-ShanghaiTech collaboration project and the Engineering and Physical Sciences Research Council (projects EP/N032128/1 and EP/X015793/1), the JSPS KAKENHI (Grant Numbers 21H05233 and 23H02052) and World Premier International Research Center Initiative (WPI), MEXT, Japan, and the Deutsche Forschungsgemeinschaft (Project No. 328545488; TRR 227, Project A03).

https://oar.a-star.edu.sg/communities-collections/articles/20567

1616-301X
1616-3028

Institute of Materials Research and Engineering