CC BY 4.0 UnportedBastien, G.Garbarino, G.Yadav, R.Martinez-Casado, F.J.Beltrán, Rodríguez, R.Stahl, Q.Kusch, M.Limandri, S.P.Ray, R.Lampen-Kelley, P.Mandrus, D.G.Nagler, S.E.Roslova, M.Isaeva, A.Doert, T.Hozoi, L.Wolter, A.U.B.Büchner, B.Geck, J.Van Den Brink, J.2020-07-202020-07-202018https://doi.org/10.34657/3673https://oa.tib.eu/renate/handle/123456789/5044Magnetization and high-resolution x-ray diffraction measurements of the Kitaev-Heisenberg material α-RuCl3 reveal a pressure-induced crystallographic and magnetic phase transition at a hydrostatic pressure of p∼0.2 GPa. This structural transition into a triclinic phase is characterized by a very strong dimerization of the Ru-Ru bonds, accompanied by a collapse of the magnetic susceptibility. Ab initio quantum-chemistry calculations disclose a pressure-induced enhancement of the direct 4d-4d bonding on particular Ru-Ru links, causing a sharp increase of the antiferromagnetic exchange interactions. These combined experimental and computational data show that the Kitaev spin-liquid phase in α-RuCl3 strongly competes with the crystallization of spin singlets into a valence bond solid.enghttps://creativecommons.org/licenses/by/4.0/530Chemical bondingFrustraded magnetismMagnetic interactionsPressure effectsSpin-orbit couplingArticle