Jeong Seung Gyo, Lee Seungjun, Lin Bonnie, Yang Zhifei, Choi In Hyeok, Oh Jin Young, Song Sehwan, Lee Seung Wook, Nair Sreejith, Choudhary Rashmi, Parikh Juhi, Park Sungkyun, Choi Woo Seok, Lee Jong Seok, LeBeau James M, Low Tony, Jalan Bharat
Department of Chemical Engineering and Materials Science, University of Minnesota-Twin Cities, Minneapolis, MN 55455.
Department of Electrical and Computer Engineering, University of Minnesota-Twin Cities, Minneapolis, MN 55455.
Proc Natl Acad Sci U S A. 2025 Jun 17;122(24):e2500831122. doi: 10.1073/pnas.2500831122. Epub 2025 Jun 11.
The anomalous Hall effect (AHE), a hallmark of time-reversal symmetry breaking, has been reported in rutile RuO, a debated metallic altermagnetic candidate. Previously, AHE in RuO 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/ nm RuO/TiO (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 (110) thin films. These findings establish ultrathin RuO as a platform for strain-engineered magnetism and underscore the transformative potential of epitaxial design in advancing spintronic technologies.
反常霍尔效应（AHE）是时间反演对称性破缺的一个标志，已在金红石型RuO₂中被报道，RuO₂是一种备受争议的金属反铁磁候选材料。此前，RuO₂中的反常霍尔效应仅在极高磁场（约50 T）下的应变弛豫厚膜中被观测到。然而，在具有独特各向异性电子结构的超薄应变薄膜中，尚无相关报道，这可能是由于无序和缺陷抑制了金属性，从而阻碍了其检测。在此，我们证明了通过混合分子束外延生长的2纳米TiO₂/1纳米RuO₂/TiO₂（110）超薄全应变异质结构保留了金属性，并在显著更低的磁场（<9 T）下表现出可观的反常霍尔效应。密度泛函理论计算表明，外延应变稳定了非补偿磁基态，并重新配置了RuO₂（110）薄膜中的磁有序。这些发现确立了超薄RuO₂作为应变工程磁性的一个平台，并强调了外延设计在推进自旋电子技术方面的变革潜力。
