Determining the lifetime of metastable skyrmions

The question of the lifetime of metastable skyrmions in a ferromagnetic background is of both fundamental importance and of practical significance for memory applications. We address this question for a chiral magnetic thin film with ferromagnetic exchange J, Dzyaloshinskii-Moriya interaction D, and anisotropy K in an external field B. We present results for skyrmion lifetimes based on novel numerical and variational approaches for analyzing the saddle-point in configuration-space paths that lead to skyrmion decay. Our results highlight the importance of the ratio of the film thickness L to the helical pitch length L_D=2πJ/D in understanding skyrmion decay. We show that Bloch point singularities play a crucial role in skyrmion decay even for small L/L_D. The role of anisotropy and external field in determining skyrmion size and stability will also be discussed and comparison with previous results presented.