Lifetime of metastable skyrmions in thin films of chiral magnets

Studying the lifetime of a metastable skyrmion in chiral magnetic materials is of fundamental interest and also of great importance for applications. We use a continuum field theory with exchange J, interfacial Dzyaloshinskii-Moriya interaction D, anisotropy K, and external field H, and compute the free energy barrier for the destruction for a skyrmion, using harmonic transition state theory (HTST) to take into account entropic effects. We show that the nature of the saddle point configuration changes from a Bloch point singularity in the 2D limit to a chiral bobber beyond a certain thickness in thin films. We discuss how the size and lifetime of metastable skyrmions vary across the (KJ/D², HJ/D²) phase diagram for the case of films with perpendicular magnetic anisotropy.