Time-reversal symmetry breaking is the basic physics concept underpinning many magnetic topological phenomena such as the anomalous Hall effect (AHE) and its quantized variant. The AHE has been primarily accompanied by a ferromagnetic dipole moment, which hinders the topological quantum states and limits data density in memory devices, or by a delicate noncollinear magnetic order with strong spin decoherence, both limiting their applicability. A potential breakthrough is the recent theoretical prediction of the AHE arising from collinear antiferromagnetism in an anisotropic crystal environment. This new mechanism does not require magnetic dipolar or noncollinear fields. However, it has not been experimentally observed to date. Here we demonstrate this unconventional mechanism by measuring the AHE in an epilayer of a rutile collinear antiferromagnet RuO2. The observed anomalous Hall conductivity is large, exceeding 300 S/cm, and is in agreement with the Berry phase topological transport contribution. Our results open a new unexplored chapter of time-reversal symmetry breaking phenomena in the abundant class of collinear antiferromagnetic materials.
@article{arxiv.2002.08712,
title = {Observation of the Anomalous Hall Effect in a Collinear Antiferromagnet},
author = {Zexin Feng and Xiaorong Zhou and Libor Šmejkal and Lei Wu and Zengwei Zhu and Huixin Guo and Rafael González-Hernández and Xiaoning Wang and Han Yan and Peixin Qin and Xin Zhang and Haojiang Wu and Hongyu Chen and Zhengcai Xia and Chengbao Jiang and Michael Coey and Jairo Sinova and Tomáš Jungwirth and Zhiqi Liu},
journal= {arXiv preprint arXiv:2002.08712},
year = {2022}
}