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@PHDTHESIS{Kurz:30593,
      author       = {Kurz, Philipp},
      title        = {{N}on-collinear magnetism at surfaces and in ultrathin
                      films},
      volume       = {3832},
      school       = {Techn. Hoch. Aachen},
      type         = {Dr. (FH)},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {PreJuSER-30593, Juel-3832},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {IV, 207 p.},
      year         = {2001},
      note         = {Record converted from VDB: 12.11.2012; Aachen, Techn.
                      Hoch., Diss., 2000},
      abstract     = {A full-potential linearized augmented plane-wave (FLAPW)
                      electronic structure method was developed to investigate
                      non-collinear magnetism in bulk systems, surfaces, and thin
                      films on the basis of the vector spin-density formulation of
                      the local density approximation (LDA) and the generalized
                      gradient approximation (GGA) to the density functional
                      theory (DFT). To allow the investigation of a large set of
                      relevant magnetic spin-structures, two extensions that go
                      beyond the treatment of periodic and stationary magnetic
                      states were implemented: (i) Arbitrary non-collinear
                      periodic magnetic configurations, which are not the magnetic
                      ground state or a stationary state of the system under
                      consideration, can be treated due to the extension of the
                      density functional equations to constrain the local magnetic
                      moments to any given direction. (ii) Commensurate and
                      incommensurate spiral (or helical) spindensity waves can be
                      treated due the extension of the vector spin-density FLAPW
                      method on the basis of a generalized Bloch theorem. A
                      detailed account of the implementation is given and the
                      importance of various approximations used are discussed.
                      This method was applied to the problem of topological
                      frustration of a two-dimensional antiferromagnet on a
                      triangular lattice. We performed self-consistent
                      calculations for the 3d transition-metal monolayers V, Cr,
                      Mn, and Fe on the (111) oriented surfaces of Cu and Ag,
                      investigating the magnetism, the interlayer relaxation, and
                      the energetics of a nearly complete set of magnetic states.
                      We found an amazing variety of different magnetic ground
                      states: ferromagnetism for Fe/Cu(111) and Fe/Ag(111);
                      row-wise antiferromagnetism for Mn/Ag(111); a coplanar
                      non-collinear periodic 120° Néel structure for V/Ag(111),
                      Cr/Cu(111) and Cr/Ag(111) ; and for Mn/Cu(111) a new complex
                      three-dimensional non-collinear spin structure, a socalled
                      3Q state, shown on the next page. By comparison with model
                      Hamiltonians we conclude that any realistic description of
                      two-dimensional itinerant antiferromagnets on a triangular
                      lattice requires exchange interactions beyond the nearest
                      neighbors and also exchange interactions beyond the
                      Heisenberg model (i.e. 4-spin and biquadratic interactions).
                      Bulk and surface calculations for hcp Gd and the Gd(0001)
                      surface were performed. Comparing different methods to treat
                      the localized 4f states, which represent a challenge for
                      first-principle theory, we show that it is crucial to remove
                      the unphysical density of states due to the minority 4f
                      electrons at the Fermi energy obtained in both LDA and GGA,
                      in order to predict the magnetic ground state correctly. We
                      carried out spin-spiral calculations to model the effect of
                      magnetic excitations, i.e. temperature, on the electronic
                      structure of the Gd(0001) surface. In the ferromagnetic
                      ground state we found a double peak structure in the local
                      density of states, due to the spin-split d$_{z^{2}}$ surface
                      state of Gd, which is probed by scanning tunneling
                      spectroscopy (STS) experiments. With increasing spin-spiral
                      q-vector, corresponding to increasing temperature, the
                      splitting of the two peaks decreases and finally vanishes,
                      while the valence magnetic moment remains finite. Hence, the
                      vanishing splitting cannot be taken as support for the
                      applicability of a pure Stoner model.},
      cin          = {IFF-IEE},
      cid          = {I:(DE-Juel1)VDB38},
      pnm          = {Elektronische Struktur von Festkörpern, Oberflächen und
                      Schichtsystemen},
      pid          = {G:(DE-Juel1)FUEK52},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/30593},
}