Dresden 2017 – scientific programme
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MA: Fachverband Magnetismus
MA 47: Spin Hall Effects and Skyrmions I
MA 47.4: Talk
Thursday, March 23, 2017, 10:15–10:30, HSZ 04
Annihilation of magnetic skyrmions by quantum tunneling — •Sergei Vlasov1,2, Pavel F. Bessarab1,2, Igor S. Lobanov2, Maria Potkina3, Valery M. Uzdin2,3, and Hannes Jónsson1 — 1University of Iceland, Reykjavík, Iceland — 2University ITMO, St. Petersburg, Russia — 3St. 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.