Since the discovery of Hall effect by Edwin Hall in 1879, there have been several variations: the anomalous Hall effect in ferromagnets, quantum Hall effect in the two-dimensional electron gas, the spin Hall effect from spin imbalance, the quantum spin Hall effect in two-dimensional topological insulators, and the quantum anomalous Hall effect in magnetic topological insulators. 

The topological Hall effect is another variation, resulting from the real-space spin chirality. It has been observed in complex magnetic materials or ferromagnet/strong spin−orbit-coupled system bilayers. As the interest on dissipationless topological electronics explodes, the occurrence of the topological Hall effect in new systems or by an unexpected mechanism becomes important.

A team led by Prof. Seung-Hyun Chun (Sejong University) discovered a robust topological Hall effect from the proximity of a noncoplanar antiferromagnet. Molecular beam epitaxy has been utilized to fabricate heterostructures of a ferromagnetic metal Cr2Te3 and a noncoplanar antiferromagnet Cr2Se3. Prof. Chun said that, “ferromagnet/antiferromagnet bilayers are well-known systems, famous for the exchange bias phenomena. However, the topological Hall effect was observed for the first time in these systems. We expect that skyrmions would be found and manipulated more easily, opening the era of topological spintronics.”

[Reference] Jeon J. et al., (2022) “Emergent topological Hall effect from exchange coupling in ferromagnetic Cr2Te3/noncoplanar antiferromagnetic Cr2Se3 bilayers”, ACS Nano, https://doi.org/10.1021/acsnano.2c00025

[Main Author] Jae Ho Jeon (Sejong University), Seung-Hyun Chun (Sejong University)

* Contact : schun@sejong.ac.kr