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@PHDTHESIS{Parlak:892386,
      author       = {Parlak, Umut},
      title        = {{O}ptically induced magnetization reversal in {C}o/{P}t
                      multilayers: {R}ole of domain wall dynamics},
      volume       = {232},
      school       = {Universität Duisburg},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2021-02047},
      isbn         = {978-3-95806-536-9},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {ix, 162, XII S.},
      year         = {2021},
      note         = {Universität Duisburg, Diss., 2021},
      abstract     = {All-optical switching (AOS) of magnetization has been
                      attracting an increasing attention due to the promising
                      application prospects in magnetic data recording technology.
                      Since the first demonstration in 2007, AOS has been observed
                      in a limited range of materials. Among them, the
                      ferromagnetic Co/Pt multilayer system comes to the forefront
                      owing to its unique magnetic and magneto-optical properties.
                      In the present project, we investigated optically induced
                      magnetization reversal mechanisms in [Co/Pt]$_{N}$
                      multilayers depending on the number of bilayers N and the
                      laser beam properties. The multilayers were grown using
                      magnetron sputtering technique at precisely controlled
                      conditions to maintain sub-nanometer thickness precision and
                      reduced interface roughness. Imaging of optically induced
                      magnetic domains was performed, using optical microscopy
                      based on magneto-optical Kerr effect (MOKE), during laser
                      illumination. We also employed photoemission electron
                      microscope for imaging with enhanced lateral resolution and
                      element selectivity. Our detailed investigation of optically
                      induced domains revealed that AOS in [Co/Pt]$_{N}$ is only
                      possible in a well defined laser influence interval
                      associated with the Curie temperature of the sample.
                      Moreover, we confirmed that helicity-dependent AOS requires
                      multiple laser pulses as well as a fine tuning of the laser
                      beam parameters. In order to further investigate the effect
                      of laser-induced heating on AOS, we illuminated the samples
                      using different laser repetition rates at different
                      temperatures. These experiments allowed us to develop a
                      model based on domain wall dynamics induced by thermal
                      gradient due to the Gaussian intensity profile of the laser
                      beam. We discuss the AOS mechanisms within the framework of
                      this model. In order to gain a detailed insight in AOS, we
                      studied ultrafast demagnetization dynamics of [Co/Pt]$_{3}$
                      multilayers using a time-resolved MOKE system. We measured
                      characteristic demagnetization and recovery times as a
                      function of the laser influence. Experiments showed that the
                      magnetization quenches within $\sim$300 fs and relaxation
                      occurs in two different timescales pointing towards multiple
                      processes governing the relaxation. Our extensive study of
                      ferromagnetic [Co/Pt]$_{N}$ multilayers and their magnetic
                      response to the femtosecond laser pulses contribute to a
                      clearer physical picture of laser-induced AOS in
                      ferromagnetic multilayers.},
      cin          = {PGI-6},
      cid          = {I:(DE-Juel1)PGI-6-20110106},
      pnm          = {522 - Quantum Computing (POF4-522)},
      pid          = {G:(DE-HGF)POF4-522},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/892386},
}