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MA: Fachverband Magnetismus
MA 14: PhD Focus Session: What about the lattice? Lessons from (ultrafast) magnetism
MA 14.4: Hauptvortrag
Dienstag, 10. März 2026, 11:35–12:05, HSZ/0002
Inertial Spin Dynamics: A Signature of Non-Markovian Interactions in Ferromagnets — •Vivek Unikandanunni1,5, Felix Hartmann2, Matias Bargheer2, Eric Fullerton3, Stefano Bonetti4,5, and Janet Anders2 — 1Institute of Applied Physics, University of Bern,Switzerland — 2Institute of Physics and Astronomy, University of Potsdam, Germany — 3Center for Memory and Recording Research, University of California San Diego, USA — 4Department of Molecular Sciences and Nanosystems, Ca Foscari University of Venice, Italy — 5Department of Physics, Stockholm University, Stockholm, Sweden
We report direct experimental observation of intrinsic inertial spin dynamics in ferromagnetic thin films, manifested as a damped THz frequency oscillation of the magnetization. Using a broadband tabletop THz source, we resonantly drive epitaxial cobalt and directly measure the frequency and relaxation time of the inertial response, which is well described by the inertial Landau-Lifshitz-Gilbert (LLG) equation. We find that the frequency and relaxation time of the inertial dynamics are dependent on the structural symmetry of the sample.
Broadband measurements further reveal a multi-peaked magnetic spectrum that cannot be captured by the inertial LLG alone. An open-quantum-system approach incorporating spin-phonon coupling through a memory kernel yields a non-Markovian LLG equation that reproduces the full experimental spectra demonstrating the fundamental role of non-Markovian memory effects in ultrafast spin dynamics.
Keywords: Inertial spin dynamics; THz pump; Non Markovian dynamics; Spin-phonon interaction; Landau-Lifshitz-Gilbert