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MA: Fachverband Magnetismus
MA 23: Magnonics II
MA 23.1: Talk
Wednesday, March 20, 2024, 09:30–09:45, EB 107
Dipolar interactions and critical dynamics in Ni — •Lukas Beddrich1, Johanna K. Jochum1, Steffen Säubert2, 3, Christian Franz4, and Peter Böni5 — 1Research Neutron Source Heinz Maier-Leibnitz (FRM II), Technical Universtity of Munich, Garching, Germany — 2Physik-Department E51, Technische Universität München, Garching, Germany — 3Department of Physics, Colorado State University, Fort Collins, USA — 4Jülich Centre for Neutron Science JCNS-MLZ, Forschungszentrum Jülich GmbH Outstation at MLZ FRM II, Garching, Germany — 5Physik-Department E21, Technische Universität München, Garching, Germany
The spin wave dispersion of an isotropic ferromagnet is described by the Holstein-Primakoff theory, which takes dipolar interactions into account. At low q, the dispersion shows linear behavior instead of ESW∝ q2, which would be expected. This is attributed to the long-range dipolar interaction between the magnetic moments. The subtle influence of these interactions on the magnon spectrum can be expressed by the dipolar wave vector qD.
Utilizing the modern MIEZE method, a neutron resonance spin-echo technique, we investigated the critical spin dynamics in nickel above and below TC. The measruements were performed at small momentum and energy transfer, reaching an energy resolution that has not been achieved before.
Our results show excellent agreement with spin wave and dynamical scaling theory. However, due to the improved resolution, the measurements strongly suggest qD to be smaller than previously reported.
Keywords: magnetism; dipolar interactions; high resolution neutron spectroscopy; critical dynamics; spin waves