# Dresden 2017 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 38: Electron Theory of Magnetism and Correlations

### MA 38.3: Vortrag

### Mittwoch, 22. März 2017, 10:00–10:15, HSZ 403

**The frozen magnon method beyond the long-wave approximation** — •Adam Jakobsson — Luleå University of Technology, Luleå, Sweden

The magnetic force theorem provides convenient ways to study exchange interactions in magnetic systems since it gives access to total energy differences between different magnetic states from non-self-consistent density functional theory calculations. This enables the efficient mapping of the total energy of the system as a function of the directions of the atomic moments in a Heisenberg model. However, it is well known that short range interactions in itinerant magnetic systems are poorly described with the conventional use of the theorem. In order to overcome this deficiency, numerous strategies have been developed over the years. We propose a two-step procedure and show that only by adding pre-converged constraining fields to non-self-consistent spin-spiral total energy calculations we obtain results that match self-consistent calculations. With this procedure, we can now do frozen magnon calculations which go beyond the long-wave approximation and thus properly describe the energy landscape of itinerant magnets. As a consequence only the exchange parameters from the non-self-consistent two-step procedure are in quantitative agreement with self-consistently derived exchange parameters. We exemplify this for three different systems: bcc Fe, fcc Ni and FeCo.