Ruthenium compounds serve as a platform for fundamental concepts such as spin-triplet superconductivity1, Kitaev spin liquids2,3,4,5 and solid-state analogues of the Higgs mode in particle physics6,7. However, basic questions about the electronic structure of ruthenates remain unanswered, because several key parameters (including Hund’s coupling, spin–orbit coupling and exchange interactions) are comparable in magnitude and their interplay is poorly understood, partly due to difficulties in synthesizing large single crystals for spectroscopic experiments. Here we introduce a resonant inelastic X-ray scattering (RIXS)8,9 technique capable of probing collective modes in microcrystals of 4d electron materials. We observe spin waves and spin-state transitions in the honeycomb antiferromagnet SrRu2O6 (ref. 10) and use the extracted exchange interactions and measured magnon gap to explain its high Néel temperature11,12,13,14,15,16. We expect that the RIXS method presented here will enable momentum-resolved spectroscopy of a large class of 4d transition-metal compounds.
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The data sets generated during and/or analysed during the current study are available from the corresponding author upon reasonable request.
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The authors thank I. I. Mazin and Y. L. Xie for stimulating discussions. The project was supported by the European Research Council under advanced grant no. 669550 (Com4Com). The authors thank DESY, a member of the Helmholtz Association HGF, for the provision of experimental facilities. The experiments were carried out at beamlines P01 and P09 of PETRA III at DESY. H.S. and K.U. acknowledge financial support from the JSPS Research Fellowship for Research Abroad. H.S. is partially supported by the Alexander von Humboldt Foundation.
The authors declare no competing interests.
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Suzuki, H., Gretarsson, H., Ishikawa, H. et al. Spin waves and spin-state transitions in a ruthenate high-temperature antiferromagnet. Nat. Mater. 18, 563–567 (2019). https://doi.org/10.1038/s41563-019-0327-2
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