Measurements and calculations on CeNiAsO point to a tilted antiferromagnetic state with a small magnetic component outside the main spin plane. The authors call it a candidate “p-wave magnet,” and their calculations retain odd-parity spin-split bands whose splitting is strongest at an intermediate tilt.
The local evidence for a tilted order
The work combined 75As nuclear-quadrupole resonance and nuclear-magnetic-resonance measurements with high-field Hall-effect and magnetization measurements on CeNiAsO. Zero-field NQR used approximately 500 milligrams of powder; NMR used 19 aligned single-crystal pieces, while separate single-crystal samples were used for transport and magnetization.
Below TN2, the NQR signal split from one peak into two, which the authors interpreted as a lattice-matched alternating spin pattern: a commensurate antiferromagnetic phase. The fitted internal field at the arsenic site was about 0.213 tesla, at roughly 44 degrees from the principal axis set by the local electric-field gradient.
NMR central-peak-splitting calculations selected an internal-field azimuth of 26.5 degrees. Magnetic-structure refinement gave moment angles of 8.2 degrees and 37.5 degrees and an out-of-plane component of about 0.05 μB; the sign of that component alternates along the crystal’s a axis, defining what the paper calls the CAFMz arrangement.
The authors describe the resulting order as tilted and coplanar, with the moments occupying a new spin plane and the spin-polarization axis deviating from the crystallographic c axis. This geometry is the basis for their candidate tilted p-wave-magnet interpretation.
Spin splitting and Hall signals
To examine the electronic side of the picture, the study used DFT+U, a computer-based electronic-structure calculation, with U = 5.0 eV and J = 2.0 eV. The moment directions were constrained, and Wannier functions were used for the anomalous Hall-conductivity calculation.
Across modeled canting angles, the calculations retained robust non-relativistic odd-parity spin-split bands. In plain terms, the modeled electronic bands stayed separated by spin in an odd-parity pattern. The calculated splitting measure ΔS rose non-monotonically, peaked near 32 degrees at 23% above the non-canted case, and then diminished at 90 degrees.
Hall measurements offered a separate test of the magnetic phases. The reported ordinary Hall coefficient was RH = 2.9(1) × 10−10 m3/C. After the ordinary contribution was separated, an anomalous Hall effect, or AHE, appeared only in the CAFMz phase and disappeared above TN2.
Raw Hall data showed two hysteresis loops well below TN2, a weak single loop at 5–6 K near TN2 and no AHE above TN2 in the incommensurate-antiferromagnetic or paramagnetic regimes.
The high-field picture remains provisional
At high field, NMR splitting changed little below 12 tesla but fell rapidly above 13 tesla. The onset agreed with the first AHE loop, and the authors treated the change as a signature of moment reorientation.
That interpretation remains inferred rather than directly resolved through the full field-driven process. The mechanism behind the two low-temperature AHE loops is also unclear, and the report does not give formal uncertainties for the refined moment angles, the spin-axis direction or the calculated spin-splitting enhancement.
The study is an arXiv preprint identified as arXiv:2608.19856v1 and dated 20 August 2026. The authors state that supporting data are available from the corresponding authors on request.
Paper data and sources
Original title: Tilted $p$-wave magnet candidate CeNiAsO
Authors: Zhuo Wang, Zheng Liu, Shuo Zou et al.
Journal/Repository: arXiv
Status: Preprint, not yet peer-reviewed
First online: 2026-08-20
DOI: Not available
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