# Regensburg 2019 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 36: Spin transport

### MA 36.3: Vortrag

### Mittwoch, 3. April 2019, 15:30–15:45, H53

**Limits of collective spin transport in easy-plane magnets** — •Martin Evers and Ulrich Nowak — University of Konstanz, D-78457 Konstanz

Within certain limits, magnetism can be described by continuous field-theory, i.e. by the micromagnetic framework. The magnetic equations are rather complex since these comprise all non-linearities of the Landau-Lifshitz-Gilbert equation; but for special systems, e.g. easy-plane magnets with small out-of-plane component the equations reduce to something showing almost the same mathematical structure as the Gross-Pitaevski equation describing the time evolution of a Bose condensate—and therefore superfluidity. Because of this very resemblance, transport in such magnets is called “spin superfluidity” [1,2], although there is one mayor difference: a damping term resulting from Gilbert damping, unavoidably leading to dissipation in the spin superfluid. However, this damping can be quite small.

Our work rests on atomistic spin simulations of easy-plane ferro- and antiferromagnets, carried out within the limits of the analytical theory of the field equations and beyond. This approach allows especially to test limits of this kind of transport—e.g. with respect to a finite temperature, high driving strengths, or disorder—presented in this talk.

[1] S. Takei et al., Phys. Rev. Lett. **112**, 227201 (2014)

B. Flebus et al., Phys. Rev. Lett. **116**, 117201 (2016)