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@INBOOK{Friedrich:860667,
      author       = {Friedrich, Christoph and Müller, Mathias C. T. D. and
                      Blügel, Stefan},
      title        = {{M}any-{B}ody {S}pin {E}xcitations in {F}erromagnets from
                      {F}irst {P}rinciples},
      address      = {Cham},
      publisher    = {Springer International Publishing},
      reportid     = {FZJ-2019-01334},
      pages        = {1-39},
      year         = {2019},
      comment      = {Handbook of Materials Modeling / Andreoni, Wanda (Editor) ;
                      Cham : Springer International Publishing, 2019, Chapter 74-2
                      ; ISBN: 978-3-319-42913-7 ; doi:10.1007/978-3-319-42913-7},
      booktitle     = {Handbook of Materials Modeling /
                       Andreoni, Wanda (Editor) ; Cham :
                       Springer International Publishing,
                       2019, Chapter 74-2 ; ISBN:
                       978-3-319-42913-7 ;
                       doi:10.1007/978-3-319-42913-7},
      abstract     = {Electronic spin excitations are low-energy excitations that
                      influence the properties of magnetic materials
                      substantially. Two types of spin excitations can be
                      identified, single-particle Stoner excitations and
                      collective spin-wave excitations. They can be treated on the
                      same footing within many-body perturbation theory. In this
                      theory, the collective spin excitations arise from the
                      correlated motion of electron-hole pairs with opposite
                      spins. We present the theory in detail and discuss several
                      aspects of an implementation within the full-potential
                      linearized augmented plane-wave method. The pair propagation
                      is described by the transverse magnetic susceptibility,
                      which we calculate from first principles employing the
                      ladder approximation for the T matrix. The four-point T
                      matrix is represented in a basis of Wannier functions. By
                      using an auxiliary Wannier set with suitable Bloch
                      character, the magnetic response function can be evaluated
                      for arbitrary k points, allowing fine details of the
                      spin-wave spectra to be studied. The energy of the acoustic
                      spin-wave branch should vanish in the limit k →0, which
                      is a manifestation of the Goldstone theorem. However, this
                      condition is often violated in the calculated acoustic
                      magnon dispersion, which can partly be traced back to the
                      choice of the Green function. In fact, the numerical gap
                      error is considerably reduced when a renormalized Green
                      function is used. As an alternative simple correction
                      scheme, we suggest an adjustment of the Kohn-Sham exchange
                      splitting. We present spin excitation spectra for the
                      elementary ferromagnets Fe, Co, and Ni as illustrative
                      examples and compare to model calculations of the
                      homogeneous electron gas},
      cin          = {IAS-1 / PGI-1 / JARA-FIT / JARA-HPC},
      cid          = {I:(DE-Juel1)IAS-1-20090406 / I:(DE-Juel1)PGI-1-20110106 /
                      $I:(DE-82)080009_20140620$ / $I:(DE-82)080012_20140620$},
      pnm          = {142 - Controlling Spin-Based Phenomena (POF3-142) / 143 -
                      Controlling Configuration-Based Phenomena (POF3-143)},
      pid          = {G:(DE-HGF)POF3-142 / G:(DE-HGF)POF3-143},
      typ          = {PUB:(DE-HGF)7},
      doi          = {10.1007/978-3-319-42913-7_74-3},
      url          = {https://juser.fz-juelich.de/record/860667},
}