Parts | Days | Selection | Search | Updates | Downloads | Help
MA: Fachverband Magnetismus
MA 26: Micromagnetism / Computational Magnetics
MA 26.5: Talk
Wednesday, March 28, 2012, 11:45–12:00, H 0112
Temperature-dependent Heisenberg exchange coupling constants from linking electronic-structure calculations and Monte Carlo simulations — •Danny Böttcher1,2, Arthur Ernst1, and Jürgen Henk1,2 — 1Max Planck Institute of Microstructure Physics, Halle, Germany — 2Martin Luther University Halle-Wittenberg, Halle, Germany
In various theoretical approximations Heisenberg exchange coupling constants Jij are calculated for zero temperature and, therefore, provide e.g. too small a critical temperature TC in comparison to the experimental value. In contrast, Jij computed within the disordered local moments (DLM) formalism (i. e. for a paramagnetic sample), overestimate TC. This mismatch leads to the idea of temperature-dependent exchange parameters.
We propose a method to calculate the temperature dependence of Jij [1]. Within the DLM formalism, the magnetization and the Jij are computed from first principles for any concentration c of the magnetic constituents. The exchange coupling constants are then used in Monte Carlo (MC) simulations to compute the temperature dependence of the magnetization for the given c. By comparing the magnetization from DLM calculations and from MC simulations we obtain a mapping of temperature versus concentration and eventually temperature-dependent Jij. The approach which is applied to bulk Fe and Co can for example improve critical exponents.
[1] D. Böttcher, A. Ernst, and J. Henk, J. Magn. Magn. Mat. 324 (2012) 610.