TY  - CHAP
AU  - Friedrich, Christoph
AU  - Şaşıoğlu, Ersoy
AU  - Müller, Mathias Christian Thomas David
AU  - Schindlmayr, Arno
AU  - Blügel, Stefan
TI  - Spin Excitations in Solids from Many-Body Perturbation Theory
VL  - 347
CY  - Berlin, Heidelberg
PB  - Springer Berlin Heidelberg
M1  - FZJ-2014-05048
SN  - 978-3-642-55067-6 (print)
T2  - Topics in Current Chemistry
SP  - 259 - 301
PY  - 2014
AB  - Collective spin excitations form a fundamental class of excitations in magnetic materials. As their energy reaches down to only a few meV, they are present at all temperatures and substantially influence the properties of magnetic systems. To study the spin excitations in solids from first principles, we have developed a computational scheme based on many-body perturbation theory within the full-potential linearized augmented plane-wave (FLAPW) method. The main quantity of interest is the dynamical transverse spin susceptibility or magnetic response function, from which magnetic excitations, including single-particle spin-flip Stoner excitations and collective spin-wave modes as well as their lifetimes, can be obtained. In order to describe spin waves we include appropriate vertex corrections in the form of a multiple-scattering T matrix, which describes the coupling of electrons and holes with different spins. The electron–hole interaction incorporates the screening of the many-body system within the random-phase approximation. To reduce the numerical cost in evaluating the four-point T matrix, we exploit a transformation to maximally localized Wannier functions that takes advantage of the short spatial range of electronic correlation in the partially filled d or f orbitals of magnetic materials. The theory and the implementation are discussed in detail. In particular, we show how the magnetic response function can be evaluated for arbitrary k points. This enables the calculation of smooth dispersion curves, allowing one to study fine details in the k dependence of the spin-wave spectra. We also demonstrate how spatial and time-reversal symmetry can be exploited to accelerate substantially the computation of the four-point quantities. As an illustration, we present spin-wave spectra and dispersions for the elementary ferromagnet bcc Fe, B2-type tetragonal FeCo, and CrO2 calculated with our scheme. The results are in good agreement with available experimental data.
LB  - PUB:(DE-HGF)7
UR  - <Go to ISI:>//WOS:000356811000008
DO  - DOI:10.1007/128_2013_518
UR  - https://juser.fz-juelich.de/record/156208
ER  -