Regensburg 2019 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 47: Quantum Magnets, Molecular Magnets and Skyrmions

TT 47.10: Talk

Wednesday, April 3, 2019, 17:30–17:45, H23

Magnon spectrum of the noncollinear antiferromagnet Mn₃Ge — •Aleksandr S. Sukhanov^1,2, Ph. Bourges³, H. C. Walker⁴, M. S. Pavlovskii⁵, K. Manna¹, C. Felser¹, and D. S. Inosov² — ¹Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany — ²Institut für Festkörperphysik, TU Dresden, 01069 Dresden, Germany — ³Laboratoire Léon Brillouin, CEA-CNRS, Université Paris-Saclay, CEA Saclay, 91191 Gif-sur-Yvette, France — ⁴ISIS Facility, STFC, Rutherford Appleton Laboratory,Didcot, Oxfordshire OX11-0QX, United Kingdom — ⁵Kirensky Institute of Physics, 660036 Krasnoyarsk, Russia

We discuss the full spin-wave spectrum of the noncollinear antiferromagnet Mn₃Ge obtained using neutron time-of-flight and triple-axis spectroscopy. The sublattice of magnetic ions in hexagonal Mn₃Ge can be viewed as two adjacent kagome layers stacked along the crystallographic [001] axis. Below T_N of 370 K the Mn atoms form the coplanar triangular 120^∘ antiferromagnetic (AFM) order. Our measurements revealed a magnon mode with a spin-wave gap of 5 meV and a very steep anisotropic dispersion. The obtained spectra allows one to build an effective model of magnetic interactions in the system. We found two coupled magnon-phonon excitations seen in the vicinity of the zone center on the energies of 14 meV and 17.5 meV. We argue that this mixed excitations represent a strong magneto-elastic coupling in Mn₃Ge.