# Dresden 2017 – wissenschaftliches Programm

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# MA: Fachverband Magnetismus

## MA 47: Spin Hall Effects and Skyrmions I

### MA 47.4: Vortrag

### Donnerstag, 23. März 2017, 10:15–10:30, HSZ 04

**Annihilation of magnetic skyrmions by quantum tunneling** — •Sergei Vlasov^{1,2}, Pavel F. Bessarab^{1,2}, Igor S. Lobanov^{2}, Maria Potkina^{3}, Valery M. Uzdin^{2,3}, and Hannes Jónsson^{1} — ^{1}University of Iceland, Reykjavík, Iceland — ^{2}University ITMO, St. Petersburg, Russia — ^{3}St. Petersburg State University, St. Petersburg, Russia

Magnetic skyrmions are localized, noncollinear spin configurations which are topological solitons. In discrete systems, a skyrmion state is separated from the ferromagnetic state by a finite energy barrier and transitions between these states can occur by jumps over the barrier or by quantum mechanical tunnelling. The rate of such transitions is an important consideration when the stability of skyrmions is assessed for data storage devices.

As the temperature is lowered, quantum tunneling becomes the dominant transition mechanism. The shift from thermally activated jumps to tunnelling is analysed and a general expression derived for the crossover temperature in terms of the second derivatives of the energy with respect to the orientations of the spin vectors at the saddle point. The expression is an extension of the theory for single spin onset temperature [S. Vlasov et al., Faraday Discussions DOI: 10.1039/c6fd00136j]. Skyrmion onset temperature is evaluated for an extened Heisenberg Hamiltonian representing a Co monolayer on Pt(111) for which the thermal jump rate has recently been calculated using a harmonic approximation to transition state theory [I.S. Lobanov et al., Phys. Rev. B 94, 174418 (2016)] and found to be 3 K.