Metallicity and anomalous Hall effect in epitaxially strained, atomically thin RuO <sub>2</sub> films
The anomalous Hall effect (AHE), a hallmark of time-reversal symmetry breaking, has been reported in rutile RuO<sub>2</sub>, a debated metallic altermagnetic candidate. Previously, AHE in RuO<sub>2</sub> was observed only in strain-relaxed thick films under extremely high magnetic fields (~50 T). Yet, in ultrathin strained films with distinctive anisotropic electronic structures, there are no reports, likely due to disorder and defects suppressing metallicity thus hindering its detection. Here, we demonstrate that ultrathin, fully strained 2 nm TiO<sub>2</sub>/<i>t</i> nm RuO<sub>2</sub>/TiO<sub>2</sub> (110) heterostructures, grown by hybrid molecular beam epitaxy, retain metallicity and exhibit a sizeable AHE at a significantly lower magnetic field (< 9 T). Density functional theory calculations reveal that epitaxial strain stabilizes a noncompensated magnetic ground state and reconfigures magnetic ordering in RuO<sub>2</sub> (110) thin films. These findings establish ultrathin RuO<sub>2</sub> as a platform for strain-engineered magnetism and underscore the transformative potential of epitaxial design in advancing spintronic technologies.
Authors
- Tony Low (ORCID: https://orcid.org/0000-0002-5759-5899)
- In Hyeok Choi (ORCID: https://orcid.org/0009-0009-6067-6196)
- James M. LeBeau (ORCID: https://orcid.org/0000-0002-7726-3533)
- Seung Gyo Jeong (ORCID: https://orcid.org/0000-0002-2504-3571)
- Woo Seok Choi (ORCID: https://orcid.org/0000-0002-2872-6191)
- Jin Young Oh (ORCID: https://orcid.org/0000-0003-2260-9960)
- Sehwan Song (ORCID: https://orcid.org/0000-0002-0398-6261)
- Zhifei Yang
- Bharat Jalan (ORCID: https://orcid.org/0000-0002-7940-0490)
- Sungkyun Park (ORCID: https://orcid.org/0000-0003-1816-310X)
- Rashmi Choudhary (ORCID: https://orcid.org/0000-0002-3558-1277)
- Sang‐Hoon Lee (ORCID: https://orcid.org/0000-0003-1710-460X)
- Seungjun Lee (ORCID: https://orcid.org/0000-0001-8197-1287)
- Jong Seok Lee (ORCID: https://orcid.org/0000-0001-6317-7944)
- B. N. Lin
- Jitendra C. Parikh (ORCID: https://orcid.org/0000-0002-2345-668X)
- Sreejith G. Nair
Institutions
- University of Minnesota (US)
- Gwangju Institute of Science and Technology (KR)
- Twin Cities Orthopedics (US)
- Pusan National University (KR)
- Massachusetts Institute of Technology (US)
- Sungkyunkwan University (KR)
Publication Details
- Journal
- Proceedings of the National Academy of Sciences
- Published
- 2025-06-11
- DOI
- https://doi.org/10.1073/pnas.2500831122
- Citations
- 13
- Primary Topic
- Electronic and Structural Properties of Oxides
- Type
- article
- Field-Weighted Citation Impact
- 6.73
Funders
- National Research Foundation of Korea
- Office of Science
- Division of Materials Research
- Air Force Office of Scientific Research