Entropy-limited topological protection of skyrmions

Abstract

Magnetic skyrmions are topologically protected whirls that decay through singular magnetic configurations known as Bloch points. We have used Lorentz transmission electron microscopy to infer the energetics associated with the topological decay of magnetic skyrmions far from equilibrium in the chiral magnet Fe${}_{1-x}$Co${}_x$Si. We observed that the life time $\tau$ of the skyrmions depends exponentially on temperature, $\tau \sim {\tau }_0{e}^{\Delta E/k_{B}T}$. The prefactor ${\tau }_0$ of this Arrhenius law changes by more than 30 orders of magnitude for small changes of magnetic field reflecting a substantial reduction of the life time of skyrmions by entropic effects and thus an extreme case of enthalpy-entropy compensation. Such compensation effects, being well-known across many different scientific disciplines, affect topological transitions and thus topological protection on an unprecedented level.

6 pages, 4 figures, 5 pages supplement, 4 figures supplement