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arXiv · 2609.18059

Disentangling Strain and Ti3+ Contributions to the Anomalous Hall Effect in Epitaxial RuO2 Films

S. G. Jeong·A. Santhosh·S. Lee·S. Sheikh·U. M. Jayathilake·T. -L. Lee·T. Low·A. X. Gray·S. A. Chambers·B. Jalan
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Abstract

The anomalous Hall effect (AHE) reported in epitaxial RuO2/TiO2 has been attributed to a strain-stabilized magnetic state, but strain can be entangled with Ru-Ti intermixing and interfacial charge redistribution, which can produce Ti3+ and potentially localized moments. Here, we disentangle these contributions using Ti-alloyed RuO2 heterostructures in which abundant Ti3+ states are retained while epitaxial strain is independently changed. The strained and relaxed films have nearly identical Ti/Ru compositions and comparable Ti3+ fractions, yet a pronounced nonlinear AHE appears only in the coherently strained film, while the relaxed heterostructure exhibits an almost linear Hall response. Spectroscopic ellipsometry further shows that the AHE-active strained state is accompanied by a reconstruction of the itinerant electronic response, including enhanced metallicity and longer carrier relaxation times. These results show that Ti3+ formation alone is insufficient to generate the anomalous Hall state and identify epitaxial strain, through its modification of the itinerant RuO2 electronic structure, as the dominant control parameter.

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S. G. Jeong, A. Santhosh, S. Lee, S. Sheikh, U. M. Jayathilake, T. -L. Lee, T. Low, A. X. Gray, S. A. Chambers, B. Jalan. 2026-09-16. Disentangling Strain and Ti3+ Contributions to the Anomalous Hall Effect in Epitaxial RuO2 Films. https://arxiv.org/abs/2609.18059

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