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@PHDTHESIS{Schweflinghaus:283061,
author = {Schweflinghaus, Benedikt Johannes},
title = {{F}irst-principles investigation of inelastic magnetic
excitations in nanostructures deposited on surfaces},
volume = {117},
school = {RWTH Aachen},
type = {Dr.},
address = {Jülich},
publisher = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
reportid = {FZJ-2016-01743},
isbn = {978-3-95806-115-6},
series = {Schriften des Forschungszentrums Jülich. Reihe
Schlüsseltechnologien / Key Technologies},
pages = {V, 204 S.},
year = {2016},
note = {RWTH Aachen, Diss., 2015},
abstract = {This thesis provides a theoretical description of inelastic
scanning tunneling spectroscopy(ISTS), using a newly
developed first-principles approach, by combining
time-dependentdensity functional theory and many-body
perturbation theory. The Korringa-Kohn-Rostoker Green
function method is utilized, since it affords a real-space
description of nanostructures, well-suited to the ISTS
context. The central quantity is the electron self-energy,
containing the interactions between the tunneling electrons
and the spin excitations of the nanostructure. This
self-energy leads to a renormalized electronic structure in
the vacuum region above the adsorbate, which can be directly
compared with the experimental ISTS signal, in the spirit of
the Tersoff-Hamann approximation. As a first application,
the developed method is applied to individual 3$\textit{d}$
transition-metal adatoms (Cr, Mn, Fe, and Co) deposited on
metallic surfaces (Cu(111) and Pt(111)). The obtained
magnetic excitation spectra for the regarded structures show
differences in the excitation lifetime and the $\textit{g}$
shift, which can be attributed to the electronic structure
of both, the adsorbate and the substrate. The calculated
theoretical inelastic spectra reveal different non-trivial
shapes of the excitation signatures, that vary with distance
to the adsorbate. Observed asymmetries in these spectra
could explain asymmetries in experimental findings.
Furthermore, some spectra show additional bound states
(satellites) that are not predictable by use of a simple
Heisenberg model. For Fe and Co adatoms on Pt(111) the
impact of hydrogen contamination on the excitation spectrum
is investigated. In agreement to experimental findings, the
presence or absence of hydrogen has a significant impact on
the shape of the excitation spectrum. In addition to the
above analysis, we also consider clusters of two or more
3$\textit{d}$ transition-metal adatoms deposited on the
Cu(111) surface, investigating the resulting magnetic
excitation spectra. The magnetic moments are coupled by the
exchange interaction which results in different excitation
modes of acoustic and optical character. The obtained
excitation spectra depend on the regarded adatom species,
the interatomic distance, the alignment of the magnetic
moments, the number of involved atoms, as well as the
arrangement on the surface. A comparison of a ring and a
chain structure reveals the impact of geometrical topology
on magnetic excitations. The semiclassical
Landau-Lifshitz-Gilbert model is used to provide an
insightful interpretation of the first-principles
spin-excitation modes.},
cin = {IAS-1 / PGI-1},
cid = {I:(DE-Juel1)IAS-1-20090406 / I:(DE-Juel1)PGI-1-20110106},
pnm = {899 - ohne Topic (POF3-899)},
pid = {G:(DE-HGF)POF3-899},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
url = {https://juser.fz-juelich.de/record/283061},
}