# Dresden 2017 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 47: Spin Hall Effects and Skyrmions I

### MA 47.1: Vortrag

### Donnerstag, 23. März 2017, 09:30–09:45, HSZ 04

**Topological orbital ferromagnets** — •Jan-Philipp Hanke, Frank Freimuth, Stefan Blügel, and Yuriy Mokrousov — Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany

Spontaneous orbital magnetism in ferromagnets is conventionally explained as a key manifestation of the spin-orbit interaction lifting partially the orbital moment quenching. While such an interpretation applies to most condensed-matter systems, it fails to describe orbital magnetism in crystals exhibiting a finite *topological* orbital magnetization (TOM) without any reference to spin-orbit coupling. In these systems an emergent magnetic field rooting in the noncoplanarity of neighboring spins replaces the spin-orbit interaction as the main mechanism lifting the orbital degeneracy by coupling to the orbital degrees of freedom. The nontrivial topology of this spin texture further gives rise to the topological Hall effect, which is closely related to the TOM both from microscopic and symmetry considerations. Here, we predict from first principles a sizable magnitude of TOM and topological Hall effect (i) in the spin-compensated thin film Mn/Cu(111) and (ii) in the antiferromagnetic bulk material γ-FeMn, both of which reveal noncoplanar spin textures in real space. We demonstrate that these systems are prototypical topological orbital ferromagnets [1,2] for which the macroscopic magnetization is completely dominated by orbital magnetism prominent even in absence of spin-orbit interaction.

[1] J.-P. Hanke *et al.*, Phys. Rev. B **94**, 121114(R) (2016).

[2] J.-P. Hanke *et al.*, Sci. Rep. (submitted, 2016).