Theory of local dynamical magnetic susceptibilities from the Korringa-Kohn-Rostoker Green function method

Abstract

Within the framework of time-dependent density functional theory combined with the Korringa-Kohn-Rostoker Green function formalism, we present a real-space methodology to investigate dynamical magnetic excitations from first principles. We set forth a scheme which enables one to deduce the correct effective Coulomb potential needed to preserve the spin-invariance signature in the dynamical susceptibilities, that is, the Goldstone mode. We use our approach to explore the spin dynamics of 3d adatoms and different dimers deposited on a Cu(001) with emphasis on their decay to particle-hole pairs.

Theoretical probing of inelastic spin-excitations in adatoms on surfaces

“…Fig. 2(a) shows our calculations of the resonant response of the local moments for four adatoms on this surface [28,29]. If an external static magnetic field is applied along the initial direction of the magnetic moments, we expect from a Heisenberg model a delta function in the excitation spectrum located at the Larmor frequency, ω L = gB ext .…”

“…[28,29] we presented a computationally attractive method that allows us to address magnetic excitations from first-principles. We use the Korringa-Kohn-Rostoker (KKR) single particle Green function (GF) [31] which contains an ab-initio description of the electronic structure.…”

“…We have also explored next nearest neighbor dimers of the same 3d adatoms deposited on Cu(001) surface [28,29], starting from a ferromagnetic configuration (Fig. 2(b)).…”

“…Indeed, the following sum rule is a consequence of Goldstone's theorem (B ext = 0 and ω = 0) [28,29]:…”

“…Since these types of calculations for magnetic materials are computationally expensive, very few DFT-based calculations, even for bulk systems, were performed [19,20], and it is only recently that a few groups have undertaken the task of calculating dynamical transverse magnetic response functions for bulk materials [21][22][23], thin films [24] and adatoms or nanostructures on surfaces [28,29]. Several studies based on empirical tight binding (ETB) theory and MBPT were published [25][26][27] which, although relying on the accuracy of fitting parameters, have advanced the understanding of many effects accompanying spin-excitations.…”