Abstract
We investigate the magnetic ground state of CuNdO2, which is a delafossite with a triangular lattice of magnetic Nd3+ ions that are well separated by non-magnetic Cu spacer layers. From inelastic neutron scattering measurements of the crystal electric field, we determine the strong Ising character of the pseudo-spin 1/2 Nd3+ moments. Magnetic susceptibility and heat capacity measurements reveal the onset of long-range antiferromagnetic order at TN = 0.78 K. While the magnetic transition is definitively observed with muon spin relaxation, accompanied by the formation of a weakly dispersing spin wave excitation, no dipole-ordered moment is detected with neutron diffraction. We show that the apparent absence of a dipolar ordered moment is a consequence of the dominant Ising character of the antiferromagnetically coupled Nd3+ moments, which experience extreme frustration on the triangular lattice. Consequently, the frustration in CuNdO2 is relieved through in-plane ordering of the substantially smaller perpendicular component of the Nd3+ moments into a 120° structure, with a nearly vanishing ordered moment.
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The data that support the findings of this study are provided in the main text. The raw data is available from the corresponding author upon request.
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Acknowledgements
This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Canadian Institute for Advanced Research (CIFAR), and the Sloan Research Fellowships program. This research was undertaken thanks in part to funding from the Canada First Research Excellence Fund, Quantum Materials and Future Technologies Program. HYK acknowledges support from NSERC Discovery Grant No. 2022-04601 and the Canada Research Chairs Program No. CRC-2019-00147. The support for neutron scattering was provided by the Center for High-Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-2010792. A portion of this research used resources at the High Flux Isotope Reactor and the Spallation Neutron Source, which are DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory. The beam time was allocated to the SEQUOIA and HB-2A instruments on proposal numbers IPTS-27501 and IPTS-27487, respectively. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology. This work is partially based on experiments performed at the Swiss Muon Source SμS, Paul Scherrer Institute, Villigen, Switzerland.
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The sample was synthesized and characterized by D.R. and A.M.H. The neutron diffraction experiment was performed by D.R., A.A.A., S.A.C., and analyzed by A.M.H. Muon spin relaxation experiments were performed by D.R., T.J.H., J.A.K., and H.L., with analysis by T.J.H. Inelastic neutron scattering experiments were performed by J.G., D.R., J.P.E., M.B.S., and A.M.H. Analysis of the crystal electric field ground state was performed by J.G., B.W., and H.Y.K. Spin wave modelling was performed by B.W. and H.Y.K. The manuscript was written by J.G., B.W., H.Y.K., and A.M.H. All authors discussed the results and commented on the manuscript.
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Hae-Young Kee is an Associate Editor of npj Quantum Materials. Hae-Young Kee was not involved in the journal’s review of, or decisions related to, this manuscript. All other authors declare no competing interests.
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Gaudet, J., Reig-i-Plessis, D., Wen, B. et al. Vanishing ordered moment in the frustrated triangular lattice antiferromagnet CuNdO2. npj Quantum Mater. (2026). https://doi.org/10.1038/s41535-026-00854-y
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DOI: https://doi.org/10.1038/s41535-026-00854-y
