Origin of the two low-temperature anomalous Hall loops

Clarify the underlying mechanism responsible for the two separate anomalous Hall-effect loops observed in CeNiAsO at low temperature, using higher-field 75As NMR measurements to resolve the associated field-induced magnetic reorientation.

Background

At low temperatures well below the second Néel transition, the Hall resistivity of CeNiAsO contains two distinct hysteresis loops. The authors observe that the onset of anomalous Hall behavior coincides with a field range in which the 75As NMR peak splitting decreases rapidly, suggesting that the Ce moments reorient under high magnetic field.

However, the authors explicitly state that the mechanism producing two separate loops is unclear. They identify additional 75As NMR experiments at substantially higher fields as necessary to resolve this question and leave it for future investigation.

References

We should also admit that the underlying mechanism for the two separate AHE loops at low temperature remains unclear to us. To further clarify this issue, additional NMR experiments with much higher field will be necessary. We leave this open question for future investigation.

— Tilted $p$-wave magnet candidate CeNiAsO  (2608.19856 - Wang et al., 20 Aug 2026) in Main text, discussion accompanying Fig. 4