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MA: Fachverband Magnetismus
MA 9: Magnonics I
MA 9.11: Vortrag
Montag, 9. März 2026, 17:45–18:00, HSZ/0004
Pinch points in the dynamical spin structure factor of dipolar ferromagnets — Michal Stekiel1, Christoph Resch2, •Konrad Scharff3, Markus Garst3, and Christian Pfleiderer2 — 1Jülich Center for Neutron Science at MLZ, Jülich, Germany — 2School of Natural Sciences, Technical University Munich, Garching, Germany — 3Karlsruhe Institute of Technology, Karlsruhe, Germany
The long-range dipolar interaction gives rise to a pinch-point non-analyticity in the dynamical spin structure factor of a ferromagnet [1]. Its experimental observation is challenging because the strength of the pinch-point singularity at zero magnetic field scales both with the magnetic moment and the size of the easy-plane anisotropy. We demonstrate that suitable materials for its detection are the rare-earth diborides, ErB2 and HoB2, as they possess a large magnetic moment on the order of 10 Bohr magneton and a pronounced easy-plane anisotropy two orders of magnitude larger than their direct exchange. In both materials, we were able to resolve pinch-point singularities in energy-momentum space using inelastic neutron scattering. The experimental signatures are quantitatively reproduced by a Heisenberg model with exchange, anisotropy and dipolar interaction.
[1] Jensen, J. and Mackintosh, A.R. Rare Earth Magnetism. Clarendon Press - Oxford (1991)
Keywords: Dipole-Dipole Interactions; 4f Electron Systems; Easy-Plane Ferromagnets; Pinch-Points