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The Heisenberg Kagome Antiferromagnet (HKAF) model occupies a central place in the field of magnetic frustration. Very early on, pioneering theoretical studies highlighted its specificity even at a classical level [1]. The quantum case is even more intriguing, with a quantum spin liquid ground-state characterized by long-range entanglement and fractionalized excitations.

In this talk, I will briefly introduce the physics inherent to the Heisenberg kagome antiferromagnet and report our recent work on two new kagome materials, using complementary spectroscopic probes (NMR, muSR and inelastic neutron scattering) to investigate their spin excitations.

The first one is a classical KHAF, the S=5/2 layered monodiphosphate Li9Fe3(P2O7)3(PO4)2 [2]. Thanks to the moderate exchange interaction (J ~ 1 K) between spins, we could experimentally investigate the phase diagram of the classical model under applied fields and evidence the highly sought-after 1/3rd magnetization plateau in a kagome compound. The second one is the S=1/2 quantum KHAF Y3Cu9(OH)18OCl8, the most recent derivative of the emblematic Herbertsmithite, which does not show any dilution or interlayer defects. The slight distortion of its kagome lattice creates three symmetry-inequivalent antiferromagnetic couplings. This S=1/2 anisotropic KHAF model was recently found to host a rich phase diagram with spin-liquid and ordered ground states [3]. I will present the results of our recent investigation using NMR, μSR and neutron scattering techniques performed on single crystals [4].

[1] J. T. Chalker, P. C. W. Holdsworth, & E. F. Shender, Phys. Rev. Lett. 68, 855 (1992).
[2] E. Kermarrec, R. Kumar, G. Bernard, R. Hénaff et al., Phys. Rev. Lett. 127, 157202 (2021).
[3] M. Hering et al., npj Comput. Mater 8, 10 (2022).
[4] D. Chatterjee et al., unpublished

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