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Spin-current-mediated Rapid Magnon Localisation and Coalescence After Ultrafast Optical Pumping of Ferrimagnetic Alloys

Published

Author(s)

Ezio E. Iacocca, TianMin Liu, Alexander H. Reid, Z Fu, S Ruta, P. W. Granitzka, E Jal, S. Bonetti, A. Gray, C E. Graves, R Kukreja, Z Chen, Daniel Higley, T Chase, L L. Guyader, K Hirsch, H Ohldag, W F. Schlotter, G L. Dakovski, Giacomo Coslovich, M C. Hoffmann, S Carron, A Tsukamoto, A Kirilyuk, A V. Kimel, Th Rasing, J Stohr, R F. Evans, T Ostler, R W. Chantrell, M A. Hoefer, Thomas J. Silva, H A. Durr

Abstract

Sub-picosecond magnetisation manipulation via femtosecond optical pumping has attracted wide attention ever since its original discovery in 1996. However, the spatial evolution of the magnetisation is not yet well understood, in part due to the difficulty in experimentally probing such rapid dynamics. Here, we find evidence of a universal rapid magnetic order recovery in ferrimagnets with perpendicular magnetic anisotropy via nonlinear magnon processes. We identify magnon localisation and coalescence processes, whereby localised magnetic textures nucleate and subsequently interact and grow in accordance with a power law formalism. A hydrodynamic representation of the numerical simulations indicates that the appearance of noncollinear magnetisation via optical pumping establishes exchange-mediated spin currents with an equivalent 100% spin polarised charge current density of 107 A cm-2. Such large spin currents precipitate rapid recovery of magnetic order after optical pumping. The magnon processes discussed here provide new insights for the stabilization of desired meta-stable states.
Citation
Nature Communications
Volume
10
Issue
1

Keywords

sub-picosecond magnetization, femtosecond optical pumping, spatial evolution, magnetization, rapid dynamics, ferrimagnets, perpendicular magnetic anisotropy, nonlinear magnon processes, magnon localization, coalescence processes, noncollinear magnetization, stabilization, meta-stable states

Citation

Iacocca, E. , Liu, T. , Reid, A. , Fu, Z. , Ruta, S. , Granitzka, P. , Jal, E. , Bonetti, S. , Gray, A. , Graves, C. , Kukreja, R. , Chen, Z. , Higley, D. , Chase, T. , Guyader, L. , Hirsch, K. , Ohldag, H. , Schlotter, W. , Dakovski, G. , Coslovich, G. , Hoffmann, M. , Carron, S. , Tsukamoto, A. , Kirilyuk, A. , Kimel, A. , Rasing, T. , Stohr, J. , Evans, R. , Ostler, T. , Chantrell, R. , Hoefer, M. , Silva, T. and Durr, H. (2019), Spin-current-mediated Rapid Magnon Localisation and Coalescence After Ultrafast Optical Pumping of Ferrimagnetic Alloys, Nature Communications, [online], https://doi.org/10.1038/s41467-019-09577-0 (Accessed April 22, 2024)
Created April 15, 2019, Updated June 29, 2020