Regensburg 2010 – scientific programme
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MA: Fachverband Magnetismus
MA 30: Electron Theory of Magnetism
MA 30.5: Talk
Thursday, March 25, 2010, 18:00–18:15, H22
Ab initio spin-wave spectra of the bulk magnets Fe, Co, and Ni from many-body perturbation theory — •Ersoy Sasioglu1, Christoph Friedrich1, Arno Schindlmayr2, and Stefan Blügel1 — 1Institut für Festkörperforschung & Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich, Germany — 2Department Physik, Universität Paderborn, 33095 Paderborn, Germany
Spin excitations are of fundamental importance in many areas of condensed matter physics. First-principles calculations of spin-wave spectra have so far mostly been carried out within the frozen-magnon approach where the excitation energy is calculated by assuming a static spin-spiral configuration. We study the magnetic excitations of bulk magnets within the framework of many-body perturbation theory (MBPT) as implemented in the full-potential linearized augmented plane-wave (FLAPW) method. Starting from the GW approximation we obtain a Bethe-Salpeter equation for the magnetic susceptibility treating single-particle Stoner excitations and magnons on the same footing. We found that the spin-wave dispersion of Fe and Co exhibit gaps close to the middle of the Brillouin zone along the high symmetry directions. For Ni, the theoretical spin-wave dispersion exhibits two branches while those for Fe and Co show only one branch. Furthermore, at high energies the spin waves are heavily damped due to the coupling to single-particle Stoner excitations. In Fe the damping suppresses the spin waves in a large part of the Brillouin zone along the Γ−H−N direction. The obtained results are in good agreement with available experimental data as well as previous calculations.