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@PHDTHESIS{Jayaraman:137777,
      author       = {Jayaraman, Rajeswari},
      title        = {{H}igh-energy high-momentum surface spin waves of ultrathin
                      epitaxial 3d transition metal films},
      volume       = {68},
      school       = {Universität Duisburg-Essen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2013-04093},
      isbn         = {978-3-89336-890-7},
      series       = {Schriften des Forschungszentrums Jülich. Reihe
                      Schlüsseltechnologien / key technologies},
      pages        = {IX, 135 S.},
      year         = {2013},
      note         = {Universität Duisburg-Essen, Diss., 2013},
      abstract     = {Surface spin waves on 3d ferromagnetic films are studied in
                      the large wave vector regime with the help of a recently
                      developed high resolution electron energy loss spectrometer.
                      As a first study, face centered cubic (fcc) cobalt films
                      were prepared by the epitaxial growth of cobalt on Cu(100).
                      Spin waves were probed along the [110]- and the
                      [010]-direction with in-plane wave vectors ranging from
                      0.02nm$^{-1}$ to 0.1nm$^{-1}$. The directional anisotropy in
                      the surface spin wave dispersion is found to be very small
                      in this system. In the low wave vector regime (wave vector <
                      0.035nm$^{-1}$), standing spin wave modes are observed in
                      addition to the surface spin waves. In cobalt, like in other
                      transition metal ferromagnets, the 3d electrons are not
                      localized. Rather they form a band of considerable width
                      which offers the possibilityfor spin-flip excitations
                      (Stoner-excitations) in a wide energy-momentum range. The
                      damping of spin waves by Stoner excitations results in large
                      energy width of the spin wave signals. For the well-defined
                      spin waves of cobalt, the line-widths of the surface spin
                      wave signals were quantitatively determined. As a next step,
                      epitaxial nickel films were prepared by deposition on
                      Cu(100). In agreement with earlier unpublished work, no spin
                      wave excitation is observed in Ni by inelastic electron
                      scattering presumably due to the strong damping of the spin
                      waves. As an attempt to study the effect of nickel on cobalt
                      surface spin waves, layers of Ni were deposited on top of
                      Co/Cu(100). Spin waves are seen for up to three monolayers
                      of Ni. By a careful study of the intensity of spin waves as
                      a function of Ni layer thickness, it is proven that spin
                      waves are localized at the Co side of the Ni/Co interface.
                      The presence of Ni broadens the spin wave peak compared to
                      bare Co spin waves, indicating additional decay channels
                      provided by the nickel capping layer. The 3d-band of copper
                      is fully occupied, and hence copper has less low energy
                      excitations. As a consequence, the mean free path of
                      electrons in copper is much larger than in nickel. This
                      provided the opportunity to look at spin waves localized at
                      the Co interface through thicker layers (up to $\approx$ 12
                      layers) of copper. A similar spin wave broadening as for
                      nickel is observed for copper. One of the extensively
                      studied systems in thin film magnetism is Fe/Cu(100) due to
                      its richness in structural and magnetic phenomena. At least
                      three different magnetic phases can be stabilized depending
                      on the film thickness. In this thesis, surface spin waves of
                      three to five monolayer iron films were studied. From the
                      similarity to the surface spin wave dispersion of bcc Fe
                      films, it is concluded that the observedspin waves arise
                      from the so-called $\textit{nanomartensitic}$ phase. The
                      nanomartensitic phase is locally similar to a bcc structure,
                      however lacking the perfect long range order of the latter.
                      The spin wave dispersion measured on iron films deposited on
                      fcc Co(100) is found to be nearly identical to that of
                      Fe/Cu(100), indicating the structural similarity of the two
                      systems.},
      keywords     = {Dissertation (GND)},
      cin          = {PGI-6},
      cid          = {I:(DE-Juel1)PGI-6-20110106},
      pnm          = {422 - Spin-based and quantum information (POF2-422)},
      pid          = {G:(DE-HGF)POF2-422},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/137777},
}