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MA: Fachverband Magnetismus
MA 12: Magnetization Dynamics and Damping
MA 12.5: Vortrag
Dienstag, 18. März 2025, 10:30–10:45, H19
Evidence of relativistic field-derivative torque in nonlinear THz response of magnetization dynamics — •Arpita Dutta1, Christian Tzschaschel2,3, Debankit Priyadarshi3, Kouki Mikuni4, Takuya Satoh4,5, Ritwik Mondal6, and Shovon Pal1 — 1NISER Bhubaneswar, HBNI, Jatni, India — 2Max-Born Institute, Berlin, Germany — 3ETH Zurich, Switzerland — 4Institute of Science Tokyo, Japan — 5Quantum Research Center for Chirality, Okazaki, Japan — 6IIT (ISM) Dhanbad, India
The selective addressing of spins by terahertz (THz) electromagnetic fields via Zeeman torque is, by far, one of the most successful means of controlling magnetic excitations. Here, we show that the conventional Zeeman torque on the spin is not sufficient, rather an additional relativistic field derivative torque (FDT) is essential to realize the observed magnetization dynamics. We accomplish this by exploring the ultrafast nonlinear magnetization dynamics of a ferrimagnetic garnet when excited by two co-propagating THz pulses. Having identified the Kaplan-Kittel mode at 0.48 THz, resulting from the exchange interaction between the rare-earth and transition metal sublattices, we drive this mode to a nonlinear regime. We find that the observed nonlinear trace of the magnetic response cannot be mapped to the magnetization precession induced by the Zeeman torque, while the Zeeman torque supplemented by an additional FDT follows the experimental evidences.
[1] A. Dutta, et al., Phys. Rev. Materials 8, 114404 (2024).
[2] A. Dutta, et al., arXiv:2408.05510 (2024).
Keywords: Magnon; Ferrimagnets; Terahertz (THz) magnetization dynamics; Nonlinear 2D THz spectroscopy