Geometrical Hall effect in ferromagnet/heavy metal heterostructures

Chun-Yen Chen^1*, Tai-Sheng Huang¹, Wan-Sheng Tang¹, Yu-Hui Tang¹, Suvechhya Lamichhane², Sy-Hwang Liou², Guan-Jhou Chen³, Ssu-Yen Huang³, Xin Fan⁴, Jhen-Yong Hong⁵

¹Department of Physics, National Central University, Taoyuan 32001, Taiwan
²Department of Physics & Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
³Department of Physics, National Taiwan University, Taipei 106319, Taiwan
⁴Department of Physics & Astronomy, University of Denver, Denver, CO 80208, USA
⁵Department of Physics, Tamkang University, New Taipei City 251301, Taiwan

* Presenter:Chun-Yen Chen, email:cychen914@g.ncu.edu.tw

The geometrical Hall Effect (GHE) refers to the transverse motion of conduction electrons, induced by an emergent electromagnetic field (EEMF). This field arises from the coupling between non-trivial spin structures and electronic wave functions associated with the Berry phase [1]. The GHE has been studied separately in momentum and spin spaces, as observed in interface-induced sign reversal of the anomalous Hall Effect (AHE) [2] and skyrmion-induced topological Hall Effect (THE) [3]. Recent research has put significant effort into classifying AHE and THE [4]; however, the possibility of non-trivial spin transport connecting the composite momentum-spin space in ferromagnet/heavy metal (FM/HM) heterostructures remains underexplored. Here, we report the coexistence of THE and sign reversal AHE in Co/Pd heterostructures with varied thicknesses and repetition numbers. Magnetic force microscopy (MFM) and micromagnetic simulations provide direct evidence of topological spin textures that depend on topological Hall resistivity. The temperature dependence of Hall transport reveals the characteristics of sign reversal AHE and a wide temperature range for the skyrmion phase. This study presents a new platform for topological spintronics within conventional FM/HM heterostructures

References:
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[2] F. Wang, X. Wang, Y.-F. Zhao, D. Xiao, L.-J. Zhou, W. Liu, Z. Zhang, W. Zhao, M. H. Chan and N. Samarth, Nature communications 12 (1), 79 (2021).
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[4] G. Kimbell, C. Kim, W. Wu, M. Cuoco and J. W. Robinson, Communications Materials 3 (1), 19 (2022).

Corresponding author:
Yu-Hui Tang (yhtang@cc.ncu.edu.tw)
Jhen-Yong Hong (jyhong@mail.tku.edu.tw)

Keywords: Geometrical Hall Effect, Topological Hall effect, Anomalous Hall Effect, Skyrmion