American Journal of Modern Physics

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Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter

Received: 27 December 2017    Accepted: 09 January 2018    Published: 18 January 2018
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Abstract

When a magnetic film is excited by a femtosecond laser pulse, either with THz or with optical frequencies, then there is at least a partial demagnetization within a few hundred femtoseconds, followed by a remagnetization to the original state on a bit longer time scale. This phenomenon is caused by a complex interaction of light with quantum matter. This paper gives a review of the present knowledge of the underlying physics. It discusses first the situation of a direct change of the magnetization by its interaction with the electromagnetic wave of the laser pulse, which appears during THz laser pulses with small field amplitudes. Then it considers the situation of an indirect change which appears after THz laser pulses with large field amplitudes and after optical laser pulses. In these cases the laser photons primarily excite electrons, with subsequent modifications of their spin-angular momenta by spin-flip scatterings of these electrons at quasiparticles, either at other electrons or at phonons or at magnons. The contributions of these various spin-flip scatterings to demagnetization are investigated. Then the transfer of angular momentum from the electronic spin system to the lattice during ultrafast demagnetization is discussed by describing the lattice vibrations in terms of magnetoelastic spin-phonon modes. Finally, the effect of electronic correlations in the sense of the density-matrix theory is investigated.

DOI 10.11648/j.ajmp.20180702.12
Published in American Journal of Modern Physics (Volume 7, Issue 2, March 2018)
Page(s) 68-74
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2024. Published by Science Publishing Group

Keywords

Ultrafast Demagnetization, Femtosecond Laser Pulses, THz and Optical Frequencies, Magnetization Precession, Spin-Flip Scatterings of Electrons, Angular Momentum Transfer, Electronic Correlations

References
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Author Information
  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Max Plank Institute for Intelligent Systems, Stuttgart, Germany

  • Department of Physics and Institute of Theoretical Physics, Nanjing Normal University, Nanjing, China

  • Institute of Solid State Theory, University of Münster, Münster, Germany

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  • APA Style

    Manfred Fähnle, Michael Haag, Christian Illg, Benedikt Mueller, Weikai Weng, et al. (2018). Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter. American Journal of Modern Physics, 7(2), 68-74. https://doi.org/10.11648/j.ajmp.20180702.12

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    ACS Style

    Manfred Fähnle; Michael Haag; Christian Illg; Benedikt Mueller; Weikai Weng, et al. Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter. Am. J. Mod. Phys. 2018, 7(2), 68-74. doi: 10.11648/j.ajmp.20180702.12

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    AMA Style

    Manfred Fähnle, Michael Haag, Christian Illg, Benedikt Mueller, Weikai Weng, et al. Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter. Am J Mod Phys. 2018;7(2):68-74. doi: 10.11648/j.ajmp.20180702.12

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  • @article{10.11648/j.ajmp.20180702.12,
      author = {Manfred Fähnle and Michael Haag and Christian Illg and Benedikt Mueller and Weikai Weng and Theodoros Tsatsoulis and Haonan Huang and Johan Briones and Nicolas Teeny and Lifa Zhang and Tilmann Kuhn},
      title = {Review of Ultrafast Demagnetization After Femtosecond Laser Pulses: A Complex Interaction of Light with Quantum Matter},
      journal = {American Journal of Modern Physics},
      volume = {7},
      number = {2},
      pages = {68-74},
      doi = {10.11648/j.ajmp.20180702.12},
      url = {https://doi.org/10.11648/j.ajmp.20180702.12},
      eprint = {https://download.sciencepg.com/pdf/10.11648.j.ajmp.20180702.12},
      abstract = {When a magnetic film is excited by a femtosecond laser pulse, either with THz or with optical frequencies, then there is at least a partial demagnetization within a few hundred femtoseconds, followed by a remagnetization to the original state on a bit longer time scale. This phenomenon is caused by a complex interaction of light with quantum matter. This paper gives a review of the present knowledge of the underlying physics. It discusses first the situation of a direct change of the magnetization by its interaction with the electromagnetic wave of the laser pulse, which appears during THz laser pulses with small field amplitudes. Then it considers the situation of an indirect change which appears after THz laser pulses with large field amplitudes and after optical laser pulses. In these cases the laser photons primarily excite electrons, with subsequent modifications of their spin-angular momenta by spin-flip scatterings of these electrons at quasiparticles, either at other electrons or at phonons or at magnons. The contributions of these various spin-flip scatterings to demagnetization are investigated. Then the transfer of angular momentum from the electronic spin system to the lattice during ultrafast demagnetization is discussed by describing the lattice vibrations in terms of magnetoelastic spin-phonon modes. Finally, the effect of electronic correlations in the sense of the density-matrix theory is investigated.},
     year = {2018}
    }
    

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    AU  - Manfred Fähnle
    AU  - Michael Haag
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    AB  - When a magnetic film is excited by a femtosecond laser pulse, either with THz or with optical frequencies, then there is at least a partial demagnetization within a few hundred femtoseconds, followed by a remagnetization to the original state on a bit longer time scale. This phenomenon is caused by a complex interaction of light with quantum matter. This paper gives a review of the present knowledge of the underlying physics. It discusses first the situation of a direct change of the magnetization by its interaction with the electromagnetic wave of the laser pulse, which appears during THz laser pulses with small field amplitudes. Then it considers the situation of an indirect change which appears after THz laser pulses with large field amplitudes and after optical laser pulses. In these cases the laser photons primarily excite electrons, with subsequent modifications of their spin-angular momenta by spin-flip scatterings of these electrons at quasiparticles, either at other electrons or at phonons or at magnons. The contributions of these various spin-flip scatterings to demagnetization are investigated. Then the transfer of angular momentum from the electronic spin system to the lattice during ultrafast demagnetization is discussed by describing the lattice vibrations in terms of magnetoelastic spin-phonon modes. Finally, the effect of electronic correlations in the sense of the density-matrix theory is investigated.
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