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The Ising triangular-lattice antiferromagnet neodymium heptatantalate as a quantum spin liquid candidate

Nature Materials volume 21, pages 416–422 (2022)Cite this article

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Abstract

Disordered magnetic states known as spin liquids are of paramount importance in both fundamental and applied science. A classical state of this kind was predicted for the Ising antiferromagnetic triangular model, while additional non-commuting exchange terms were proposed to induce its quantum version—a quantum spin liquid. However, these predictions have not yet been confirmed experimentally. Here, we report evidence for such a state in the triangular-lattice antiferromagnet NdTa7O19. We determine its magnetic ground state, which is characterized by effective spin-1/2 degrees of freedom with Ising-like nearest-neighbour correlations and gives rise to spin excitations persisting down to the lowest accessible temperature of 40 mK. Our study demonstrates the key role of strong spin–orbit coupling in stabilizing spin liquids that result from magnetic anisotropy and highlights the large family of rare-earth (RE) heptatantalates RETa7O19 as a framework for realization of these states, which represent a promising platform for quantum applications.

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Fig. 1: Crystal structure and magnetic ground state of NdTa7O19.
Fig. 2: Bulk magnetic properties of NdTa7O19.
Fig. 3: Excitations and correlations in NdTa7O19.
Fig. 4: Magnetic anisotropy in NdTa7O19.
Fig. 5: Quantum SL ground state of NdTa7O19 evidenced by muon spectroscopy.

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Data availability

All data that support the findings of this study are available from the corresponding author upon reasonable request. The inelastic neutron scattering data can be found in ref. 60, the neutron diffraction data in ref. 61, the diffuse neutron scattering data in ref. 62 and the μSR data in ref. 63.

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Acknowledgements

We thank B. D. Gaulin for fruitful discussions. We acknowledge the financial support of the Slovenian Research Agency under programme no. P1-0125 and projects no. J1-2461, no. BI-US/18-20-064, no. N1-0148 and no. J2-2513. Also, we acknowledge the financial support from the Science and Engineering Research Board, and the Department of Science and Technology, India, through research grants. The National High Magnetic Field Laboratory is supported by the National Science Foundation through NSF/DMR-1644779 and the State of Florida. INS and neutron diffraction experiments at the ISIS Neutron and Muon Source were supported by beam-time allocations RB1920405 and RB2000222, respectively, while the μSR experiment was supported by the beam-time allocation RB1910518, all approved by the Science and Technology Facility Council. Diffuse magnetic scattering measurements were supported by beam-time allocation 5-32-930 approved by ILL.

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Authors and Affiliations

  1. Jožef Stefan Institute, Ljubljana, Slovenia

    T. Arh, M. Pregelj & A. Zorko

  2. Faculty of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia

    T. Arh & A. Zorko

  3. Department of Physics, Indian Institute of Technology Madras, Chennai, India

    B. Sana & P. Khuntia

  4. Quantum Centre for Diamond and Emergent Materials, Indian Institute of Technology Madras, Chennai, India

    P. Khuntia

  5. Functional Oxide Research Group, Indian Institute of Technology Madras, Chennai, India

    P. Khuntia

  6. Faculty of Civil and Geodetic Engineering, University of Ljubljana, Ljubljana, Slovenia

    Z. Jagličić

  7. Institute of Mathematics, Physics and Mechanics, Ljubljana, Slovenia

    Z. Jagličić

  8. ISIS facility, Rutherford Appleton Laboratory, Didcot, UK

    M. D. Le, P. K. Biswas & P. Manuel

  9. Institut Laue-Langevin, Grenoble, France

    L. Mangin-Thro

  10. National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL, USA

    A. Ozarowski

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Contributions

T.A. and B.S. contributed equally to this work and are both assigned first authorship of the paper. P.K. conceived the investigation of NdTa7O19, while A.Z. is the corresponding author who designed this project and supervised the experiments presented in this work. B.S. and P.K. synthesized and structurally characterized the sample. Z.J. and B.S. performed the bulk magnetic measurements. T.A., M.P. and M.D.L. conducted the INS measurements, P.M. conducted the neutron diffraction experiment, and L.M.-T. conducted the diffuse magnetic scattering experiment. M.P. analysed the neutron scattering results and performed the CEF modelling. A.Z. and A.O. performed the ESR measurements, and A.Z. analysed the results. T.A., P.K.B. and A.Z. conducted the μSR investigation; T.A. analysed the corresponding data. All authors discussed the results and the paper. A.Z. wrote the paper, with input provided by M.P. and P.K.

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Correspondence to A. Zorko.

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Supplementary Figs. 1–7, Tables I–III and Discussion.

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Arh, T., Sana, B., Pregelj, M. et al. The Ising triangular-lattice antiferromagnet neodymium heptatantalate as a quantum spin liquid candidate. Nat. Mater. 21, 416–422 (2022). https://doi.org/10.1038/s41563-021-01169-y

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