Controllable Thickness Inhomogeneity and Berry Curvature Engineering of Anomalous Hall Effect in SrRuO3 Ultrathin Films

Lingfei Wang; Qiyuan Feng; Han Gyeol Lee; Eun Kyo Ko; Qingyou Lu; Tae Won Noh

doi:10.1021/acs.nanolett.9b05206

Controllable Thickness Inhomogeneity and Berry Curvature Engineering of Anomalous Hall Effect in SrRuO₃ Ultrathin Films

Nano Lett. 2020 Apr 8;20(4):2468-2477. doi: 10.1021/acs.nanolett.9b05206. Epub 2020 Mar 26.

Authors

Lingfei Wang^{1

2}, Qiyuan Feng³, Han Gyeol Lee^{1

2}, Eun Kyo Ko^{1

2}, Qingyou Lu^{3

4}, Tae Won Noh^{1

2}

Affiliations

¹ Center for Correlated Electron Systems (CCES), Institute for Basic Science (IBS), Seoul 08826, Republic of Korea.
² Department of Physics and Astronomy, Seoul National University, Seoul 08826, Republic of Korea.
³ Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory and High Magnetic Field Laboratory of Anhui Province, Chinese Academy of Sciences, Hefei, Anhui 230031, China.
⁴ Hefei National Laboratory for Physical Sciences at the Microscale and Anhui Laboratory of Advanced Photon Science and Technology, University of Science and Technology of China, Hefei, Anhui 230026, China.

PMID: 32202801
DOI: 10.1021/acs.nanolett.9b05206

Abstract

In quantum matters hosting electron-electron correlation and spin-orbit coupling, spatial inhomogeneities, arising from competing ground states, can be essential for understanding exotic topological properties. A prominent example is Hall anomalies observed in SrRuO₃ films, which were interpreted in terms of either magnetic skyrmion-induced topological Hall effect or inhomogeneous anomalous Hall effect (AHE). To clarify this ambiguity, we systematically investigated the evolution of AHE with controllable inhomogeneities in SrRuO₃ film thickness (t_SRO). By exploiting the step-flow growth of SrRuO₃ films, we induced a microscopically ordered stripe pattern with one-unit-cell differences in t_SRO. The associated spatial distribution of momentum-space Berry curvatures enables a two-channel AHE with hump-like Hall anomalies, which can be continuously engineered according to non-integer t_SRO. We further microscopically characterized the stripe-like ferromagnetic domains and two-step magnetic switching behavior in the inhomogeneous SrRuO₃ film. These unique features can be utilized to identify the two-channel AHE model and understand its microscopic origin.

Keywords: Berry curvature; SrRuO3; anomalous Hall effect; epitaxial thin films; inhomogeneity.