Dresden 2014 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 51: Electron Theory of Magnetism

MA 51.3: Vortrag

Freitag, 4. April 2014, 10:00–10:15, HSZ 401

Ab-initio spin dynamics for clusters — •Laszlo Udvardi, Levente Rozsa, and Laszlo Szunyogh — Dept. of Theor. Phys., TU Budapest, Hungary

Ab initio atomistic spin dynamics simulations provide a way to theoretically investigate systems containing from a few dozen to a few thousand atoms. These methods are based on the numerical solution of the stochastic Landau-Lifshitz-Gilbert (LLG) equation. In most of the cases the torque driving the motion of the spins is determined by means of a Heisenberg model with ab-inito parameters.

In the present work we propose a method where the torque is calculated directly from the density functional theory without the need of underlying Heisenberg model. The electronic structure of the cluster is determined by applying the embedded cluster method using the relativistic Korringa-Kohn-Rostoker method. The torque rotating the spins in the cluster is calculated within the framework of the magnetic force theorem as the derivatives of the band energy with respect of the transverse change of the magnetization.

The method is applied for a 10 atoms long linear Co chain on Au (001) surface. The magnetic ground state is turned out to be a spin spiral due to the Dzyaloshinsky-Moriya interaction. The results of the simulations are in good agreement with the results of the analytically solvable Heisenberg chain with nearest neighbor exchange coupling. The behaviour of the switching between the two degenerate ground states was also studied by means of both ab-initio and model calculations.