Strain-tunable anomalous Hall plateau in antiferromagnet CoNb₃S₆

Antiferromagnets exhibiting the anomalous Hall effect (AHE) represent a fascinating convergence of magnetism, topology, and electronic structure. CoNb₃S₆ is an excellent example of layered antiferromagnets [1,2] that has attracted increasing attentions in recent years due to its rich physics. Nirmal et al [3] first discovered the unexpected large AHE (~27 W^-1 cm^-1) and later Giulia et al [4] found the AHE can be further enhanced in small exfoliated crystals (~400 W^-1 cm^-1). In 2020, Smejkal et al rebranded the AHE in CoNb₃S₆ as the “crystal Hall effect”, with CoNb₃S₆ being an early altermagnet candidate [5,6]. Moreover, neutron scattering measurements suggested that CoNb₃S₆ has a non-coplanar antiferromagnetic structure and the AHE should be a spontaneous topological Hall effect from spin chirality [7]. Here, we report a strain tunable anomalous Hall plateau in the antiferromagnet CoNb₃S₆, which is characterized a flat extended intermediate step of the anomalous Hall hysteresis loop. The remarkable tunability of the plateau indicates the existence of a hidden phase transition that significantly changes the magnetic anisotropy energy but not the magnetic order. As a result, the anomalous Hall plateau reflects the phase coexistence during the hidden transition, which is non-volatile and enables an unusual four-state switching of the anomalous Hall effect. We believe further investigations into the underlying mechanisms and potential applications of this strain-engineered magnetic phenomenon could contribute to the advancement and innovations in data storage and other magnetic technologies.

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[2] S. S. P. Parkin et al., Journal of Physics C: Solid State Physics 16, 2765 (1983).

[3] N. J. Ghimire et al., Nature Communications 9, 3280 (2018).

[4] G. Tenasini et al., Physical Review Research 2, 023051 (2020).

[5] L. Šmejkal et al., Science Advances 6, eaaz8809 (2020).

[6] L. Šmejkal et al., Physical Review X 12, 040501 (2022).

[7] H. Takagi et al., Nature Physics 19, 961 (2023).