Regensburg 2019 – scientific programme

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MA: Fachverband Magnetismus

MA 55: Electron theory and micromagnetism

MA 55.2: Talk

Friday, April 5, 2019, 09:45–10:00, H38

An extension of the Heisenberg Hamiltonian: temperature dependent and multi-spin exchange parameters from first principles — •Sergiy Mankovsky and Hubert Ebert — Dept. Chemistry, LMU Munich, D-81377 Munich, Germany

We will present an extension of the Heisenberg model by accounting for multi-spin exchange and temperature dependent exchange interactions calculated from first principles based on the electronic structure calculations by means of the Korringa-Kohn-Rostoker (KKR) Green function method. The temperature dependent behaviour of the exchange parameters is obtained accounting for thermal lattice vibrations and spin fluctuations treated by means of the CPA alloy theory within the alloy analogy model [1]. To calculate the multi-spin exchange interactions, we follow the approach reported previously [2], using a higher order expansion of the Green function entering the free energy expression accounting this way for a deviation of magnetic moments from a reference configuration. To demonstrate the impact of these contributions we represent results of calculations for different types of system: pure elemental materials, ordered compounds as well as alloys with chemical disorder.

[1] H. Ebert, S. Mankovsky, et al., Phys. Rev. B 91, 165132 (2015)

[2] S. Mankovsky, S. Polesya, H. Ebert, arXiv:1810.13175 (2018)