Emergent Topological Hall Effect at a Charge-Transfer Interface

Zhi Shiuh Lim; Changjian Li; Zhen Huang; Xiao Chi; Jun Zhou; Shengwei Zeng; Ganesh Ji Omar; Yuan Ping Feng; Andrivo Rusydi; Stephen John Pennycook; Thirumalai Venkatesan; Ariando Ariando

doi:10.1002/smll.202004683

Emergent Topological Hall Effect at a Charge-Transfer Interface

Small. 2020 Dec;16(50):e2004683. doi: 10.1002/smll.202004683. Epub 2020 Nov 16.

Authors

Zhi Shiuh Lim^{1

2}, Changjian Li^{1

3}, Zhen Huang^{1

2}, Xiao Chi^{2

4}, Jun Zhou², Shengwei Zeng^{1

2}, Ganesh Ji Omar^{1

2}, Yuan Ping Feng², Andrivo Rusydi^{2

4}, Stephen John Pennycook³, Thirumalai Venkatesan^{1

2

3}, Ariando Ariando^{1

2}

Affiliations

¹ NUSNNI-NanoCore, National University of Singapore, Singapore, 117411, Singapore.
² Department of Physics, National University of Singapore, Singapore, 117542, Singapore.
³ Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore.
⁴ Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore, 117603, Singapore.

PMID: 33191619
DOI: 10.1002/smll.202004683

Abstract

Exploring exotic interface magnetism due to charge transfer and strong spin-orbit coupling has profound application in the future development of spintronic memory. Here, the emergence and tuning of topological Hall effect (THE) from a CaMnO₃ /CaIrO₃ /CaMnO₃ trilayer structure are studied in detail, which suggests the presence of magnetic Skyrmion-like bubbles. First, by tilting the magnetic field direction, the evolution of the Hall signal suggests a transformation of Skyrmions into topologically-trivial stripe domains, consistent with behaviors predicted by micromagnetic simulations. Second, by varying the thickness of CaMnO₃ , the optimal thicknesses for the THE signal emergence are found, which allow identification of the source of Dzyaloshinskii-Moriya interaction (DMI) and its competition with antiferromagnetic superexchange. Employing high-resolution transmission electron microscopy, randomly distributed stacking faults are identified only at the bottom interface and may avoid mutual cancellation of DMI. Last, a spin-transfer torque experiment also reveals a low threshold current density of ≈10⁹ A m^-2 for initiating the bubbles' motion. This discovery sheds light on a possible strategy for integrating Skyrmions with antiferromagnetic spintronics.

Keywords: CaIrO3; Skyrmion-like bubbles; charge transfer; spin-orbit coupling; topological Hall effect.

Abstract

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