Regensburg 2016 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 30: Spin-Torque Phenomena
MA 30.6: Vortrag
Mittwoch, 9. März 2016, 11:15–11:30, H33
Terahertz nonlinear spin response in thulium orthoferrite — •Sebastian Baierl1, Matthias Hohenleutner1, Tobias Kampfrath2, Anatoly Zvezdin3, Alexey Kimel4, Rupert Huber1, and Rostislav Mikhaylovskiy4 — 1Department of Physics, University of Regensburg, 93053 Regensburg, Germany — 2Department of Physical Chemistry, Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin, Germany — 3Prokhorov General Physics Institute, Russian Academy of Sciences, 119991 Moscow, Russia — 4Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands
We show the first nonlinear spin response of a magnetically ordered system to intense terahertz (THz) fields. The oscillating carrier wave of ultrashort THz pulses coherently excites magnons in the canted antiferromagnet thulium orthoferrite. In its spin reorientation phase, the amplitude of the quasi-ferromagnetic mode is found to scale quadratically with the THz field, exceeding the strength of the Zeeman interaction by a factor of 7 for peak magnetic THz fields of 0.3 T. This finding marks a new regime of THz-induced spin dynamics beyond the Zeeman interaction and the first observation of a THz field-triggered magnetic nonlinearity. We assign this intriguing effect to an ultrafast, THz electric-field-driven change of the magnetic anisotropy mediated by crystal field transitions within the thulium ions. By symmetry, the latter effect is only allowed if the crystal is situated in the spin reorientation phase. This novel driving mechanism points out unforeseen routes towards THz induced magnetic switching.