22-32-201
Mattias Riepp – Institut de Physique et Chimie des Matériaux de Strasbourg – Deutsches Elektronen-Synchrotron DESY, Hamburg
Abstract
Terahertz (THz) light pulses can be used for an ultrafast coherent manipulation of the magnetization [1,2], which is among the fastest possible ways of writing magnetic information in ferromagnetic thin films [3]. Using time-resolved resonant magnetic scattering at the free-electron laser FLASH beamline BL3 [4], we gained completely new insights to the THz-driven coherent magnetization dynamics on nanometer length scales. We observe ultrafast incoherent demagnetization as well as ultrafast coherent magnetization oscillations that are governed by a time-dependent damping. This damping is determined by the time- and fluence-dependent compensation of the magnetic anisotropy energy barrier, suggesting an upper speed limit for THz-induced magnetization switching. We find that, in the presence of nanometer-sized magnetic domains, the ultrafast coherent magnetization oscillations are associated with a correlated beating of the domain walls. The overall domain structure thereby remains largely unaffected, highlighting the applicability of THz-induced magnetization switching on the nanoscale.
References
[1] T. Kampfrath, A. Sell, G. Klatt, A. Pashkin, S. Mährlein, T. Dekorsy, M. Wolf, M. Fiebig, A. Leitenstorfer, and R. Huber, Coherent terahertz control of antiferromagnetic spin waves. Nature Photonics 5(1), 31–34 (2011).
[2] S. Bonetti, M. C. Hoffmann, M.-J. Sher, Z. Chen, S.-H. Yang, M. G. Samant, S. S. P. Parkin, and H. A. Dürr, THz-Driven Ultrafast Spin-Lattice Scattering in Amorphous Metallic Ferromagnets. Physical Review Letters 117(8), 087205 (2016).
[3] I. Tudosa, C. Stamm, A. B. Kashuba, F. King, H. C. Siegmann, J. Stöhr, G. Ju, B. Lu, and D. Weller, The ultimate speed of magnetic switching in granular recording media. Nature 428(6985), 831–833 (2004).
[4] R. Pan, E. Zapolnova, T. Golz, A. J. Krmpot, M. D. Rabasovic, J. Petrovic, V. Asgekar, B. Faatz, F. Tavella, A. Perucchi et al., Photon diagnostics at the FLASH THz beamline. Journal of Synchrotron Radiation 26(3), 700–707 (2019).
