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ABSTRACT The quest for ultrafast magnetic processes has triggered a new field of research—femtomagnetism: using femtosecond laser pulses to demagnetize ferromagnetic metallic thin films.

Despite being the subject of intense research for over a decade, the underlying mechanisms that govern the demagnetization remain unclear. Here, we investigate how an ultrashort laser pulse

couples to the spin of electrons in ferromagnetic metals. It is shown that a single 50-fs laser pulse couples efficiently to a ferromagnetic film during its own propagation. This result

indicates that the material polarization induced by the photon field interacts coherently with the spins. The corresponding mechanism has its origin in relativistic quantum electrodynamics,

beyond the spin–orbit interaction involving the ionic potential. In addition, this coherent interaction is clearly distinguished from the incoherent ultrafast demagnetization associated with

the thermalization of the spins. We forecast that the corresponding coherent self-induced processes are the dawn of a new era for future research in magnetism. Access through your

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BEING VIEWED BY OTHERS ATTOSECOND MAGNETIZATION DYNAMICS IN NON-MAGNETIC MATERIALS DRIVEN BY INTENSE FEMTOSECOND LASERS Article Open access 23 March 2023 ACCELERATING ULTRAFAST MAGNETIZATION

REVERSAL BY NON-LOCAL SPIN TRANSFER Article Open access 27 January 2023 POLARISATION-DEPENDENT SINGLE-PULSE ULTRAFAST OPTICAL SWITCHING OF AN ELEMENTARY FERROMAGNET Article Open access 11

January 2022 CHANGE HISTORY * _ 16 JUNE 2009 In the version of this article originally published online, corrections were needed to: Fig. 1, right-hand Gel label should read Gsl; Fig. 2b,c,

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Article  ADS  Google Scholar  Download references ACKNOWLEDGEMENTS We thank I. Perakis for helpful discussions on coherent magnetic effects in semiconductors, and J. Arabski and M. Albrecht

for their technical support. This project was carried on thanks to the financial support of the Centre National de la Recherche Scientifique in France. AUTHOR INFORMATION AUTHORS AND

AFFILIATIONS * Institut de Physique et Chimie des Matériaux de Strasbourg, UMR 7504, CNRS, Université de Strasbourg, BP 43, 23 rue du Loess, 67034 Strasbourg Cedex 02, France Jean-Yves

Bigot, Mircea Vomir & Eric Beaurepaire Authors * Jean-Yves Bigot View author publications You can also search for this author inPubMed Google Scholar * Mircea Vomir View author

publications You can also search for this author inPubMed Google Scholar * Eric Beaurepaire View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS

J.Y.B. and M.V. designed and carried out the experiments, analysed the data and wrote the paper. E.B. supervised the samples elaboration and characterization. CORRESPONDING AUTHOR

Correspondence to Jean-Yves Bigot. RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Bigot, JY., Vomir, M. & Beaurepaire, E. Coherent ultrafast

magnetism induced by femtosecond laser pulses. _Nature Phys_ 5, 515–520 (2009). https://doi.org/10.1038/nphys1285 Download citation * Received: 09 November 2008 * Accepted: 23 April 2009 *

Published: 31 May 2009 * Issue Date: July 2009 * DOI: https://doi.org/10.1038/nphys1285 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get

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