17 research outputs found
Tuning paramagnetic spin-excitations of single adatoms
Around 50 years ago, Doniach [Proc. Phys. Soc. 91, 86 (1967)] predicted the
existence of paramagnons in nearly ferromagnetic materials, recently measured
in bulk Pd [Phys. Rev. Lett. 105, 027207 (2010)]. Here we predict the analogous
effect for single adatoms, namely paramagnetic spin-excitations (PSE). Based on
time-dependent density functional theory, we demonstrate that these overdamped
excitations acquire a well-defined peak structure in the meV energy region when
the adatom's Stoner criterion for magnetism is close to the critical point. In
addition, our calculations reveal a subtle tunability and enhancement of PSE by
external magnetic fields, exceeding by far the response of bulk paramagnons and
even featuring the atomic version of a quantum phase transition. We further
demonstrate how PSE can be detected as moving steps in the
signal of state-of-the-art inelastic scanning tunneling spectroscopy, opening a
potential route for experimentally accessing fundamental electronic properties
of non-magnetic adatoms, such as the Stoner parameter.Comment: 6 pages, 3 figure
Theoretical probing of inelastic spin-excitations in adatoms on surfaces
We review our recent work on the simulation, description and prediction of
spin-excitations in adatoms and dimers deposited on metallic surfaces. This
work done together with Douglas L. Mills, is an extension of his seminal
contribution (with Pascal Lederer) published 50 years ago on the spin-dynamics
of transition metal impurities embedded in transition metal hosts [P. Lederer,
D.L. Mills, Phys. Rev. {\bf 160}, 590 (1967)]. The main predictions of his
model were verified experimentally with state of the art inelastic scanning
tunneling spectroscopy on adatoms. Our formalism, presented in this review, is
based on time-dependent density functional theory, combined with the
Korringa-Kohn-Rostoker Green function method. Comparison to experiments is
shown and discussed in detail. Our scheme enables the description and
prediction of the main characteristics of these excitations, \emph{i.e.} their
resonance frequency, their lifetime and their behavior upon application of
external perturbations such as a magnetic field.Comment: 24 pages, invited review to the special issue "Spins at Surfaces" in
Surface Scienc
Role of Dzyaloshinskii-Moriya interaction for magnetism in transition-metal chains at Pt step edges
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