The anomalous Hall effect (AHE), a hallmark of time-reversal symmetry breaking, has been reported in rutile RuO2, a debated metallic altermagnetic candidate. Previously, AHE in RuO2 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 TiO2/t nm RuO2/TiO2 (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 non-compensated magnetic ground state and reconfigures magnetic ordering in RuO2 (110) thin films. These findings establish ultrathin RuO2 as a platform for strain-engineered magnetism and underscore the transformative potential of epitaxial design in advancing spintronic technologies.
@article{arxiv.2501.11204,
title = {Metallicity and Anomalous Hall Effect in Epitaxially-Strained, Atomically-thin RuO2 Films},
author = {Seung Gyo Jeong and Seungjun Lee and Bonnie Lin and Zhifei Yang and In Hyeok Choi and Jin Young Oh and Sehwan Song and Seung wook Lee and Sreejith Nair and Rashmi Choudhary and Juhi Parikh and Sungkyun Park and Woo Seok Choi and Jong Seok Lee and James M. LeBeau and Tony Low and Bharat Jalan},
journal= {arXiv preprint arXiv:2501.11204},
year = {2025}
}