Regensburg 2010 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
MA: Fachverband Magnetismus
MA 4: Magnetic Coupling Phenomena/ Exchange Bias
MA 4.5: Vortrag
Montag, 22. März 2010, 12:00–12:15, H22
Ab initio exchange constants for the Heisenberg model — •Adam Jakobsson1,2, Stefan Blügel1, Marjana Ležaić1, and Biplab Sanyal2 — 1Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany — 2Department of Physics and Materials Science, Uppsala University, Box 530, SE-75121 Uppsala, Sweden
Ab initio total energies of spin spirals in selected metals and insulators have been mapped to Heisenberg Hamiltonian in order to extract the exchange constants as well as Curie temperatures through a Monte Carlo algorithm. The full potential linearized augmented plane wave code FLEUR [1] was employed. A comparison is made between extracting exchange constants from a set of Fourier transforms and a least square fit to total energies. The calculations of total energy differences are approximated by the use of Andersen’s force theorem. The validity and the precision of the calculations are discussed. For strongly correlated systems such as MnO a Hubbard U is applied and additional attention is required when the force theorem is used. The benchmark materials bcc Fe, fcc Ni and rock salt MnO are covered. Fe is a metal and has long ranged interactions with Ruderman-Kittel-Kasuya-Yosida behaviour. In contrast the insulator MnO has mainly short ranged interactions. For Ni longitudinal fluctuations of magnetic moments are substantial. Finally we discuss a Hamiltonian with higher order terms and the influence they might have on magnetism of some compounds.
www.flapw.de