Topological Hall effect in Co/Pd multilayers

Chun-Yen Chen^1*, Yi-Feng Lai¹, Suvechhya Lamichhane², Ahsan Ullah², Danru Qu³, Ssu-Yen Huang⁴, Wen-Chin Lin⁵, Sy-Hwang Liou², Yu-Hui Tang¹, Jhen-Yong Hong⁶

¹Department of Physics, National Central University, Taoyuan 32001, Taiwan
²Department of Physics & Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588, USA
³Center for Condensed Matter Sciences, National Taiwan University, Taipei 106319, Taiwan
⁴Department of Physics, National Taiwan University, Taipei 106319, Taiwan
⁵Department of Physics, National Taiwan Normal University, Taipei 106209, Taiwan
⁶Department of Physics, Tamkang University, New Taipei city 251301, Taiwan

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

The topological Hall effect (THE) has been widely employed to investigate chiral spin textures, such as Skyrmion, which originates from the interfacial Dzyaloshinskii–Moriya interaction (i-DMI) between heavy-metal/ferromagnet heterostructures [1-3]. It’s known to stabilize topological spin textures by manipulating the different sign and magnitude of i-DMI in the asymmetric structures, such as asymmetric multilayers [4] and synthetic antiferromagnetic multilayers [5]. Recently, the metastable skyrmions can also be found in symmetric multilayers due to interdiffusion at the thin interface [6]. Here, we investigate room temperature THE in symmetric (Co/Pd)_N multilayer by varying the thickness of Co and repetition number (N). An unusual Hall resistance hysteresis loop with a hump appears at the critical thickness (Co = 0.55 nm) when the anomalous Hall effect (AHE) changes sign. Magnetic domain imaging confirms that the measured hump resistivity is proportional to topological charge density (n_T), which is directly related to THE. The THE, domain transformation and the contribution of i-DMI for stabilizing spin texture in symmetric multilayers will be further discussed.

REFERENCES
[1] A. Fert et al. Nature nanotechnology 8, 152 (2013)
[2] A. Neubauer et al. Physical Review Letters 102, 186602 (2009)
[3] M. Raju et al., Nature Communications 10, 696 (2019)
[4] A. Soumyanarayanan et al., Nature materials 16, 898 (2017)
[5] T. Dohi et al. Nature communications 10, 5153 (2019)
[6] P. C. Carvalho et al. Nano Letters 23, 11, 4854 (2023)

Keywords: Topological Hall effect, Magnetic Skyrmion, Dzyaloshinskii-Moriya interaction, Magnetic multilayers