Thermal stability of metastable magnetic skyrmions: Entropic narrowing and significance of internal eigenmodes

L. Desplat (Corresponding author), D. Suess, J-V. Kim, R. L. Stamps

Publications: Contribution to journalArticlePeer Reviewed

Abstract

We compute annihilation rates of metastable magnetic skyrmions using a form of Langer's theory in the intermediate-to-high damping (IHD) regime. For a Néel skyrmion, a Bloch skyrmion, and an antiskyrmion, we look at two possible paths to annihilation: collapse and escape through a boundary. We also study the effects of a curved versus a flat boundary, a second skyrmion, and a nonmagnetic defect. We find that the skyrmion's internal modes play a dominant role in the thermally activated transitions compared to the spin-wave excitations and that the relative contribution of internal modes depends on the nature of the transition process. Our calculations for a small skyrmion stabilized at zero field show that collapse on a defect is the most probable path. In the absence of a defect, the annihilation is largely dominated by escape mechanisms, even though in this case the activation energy is higher than that of collapse processes. Escape through a flat boundary is found more probable than through a curved boundary. The potential source of stability of metastable skyrmions is therefore found not to lie in high activation energies, nor in the dynamics at the transition state, but comes from entropic narrowing in the saddle point region which leads to lowered attempt frequencies. This narrowing effect is found to be primarily associated with the skyrmion's internal modes.

Original languageEnglish
Article number134407
Number of pages13
JournalPhysical Review B
Volume98
Issue number13
DOIs
Publication statusPublished - 4 Oct 2018

Austrian Fields of Science 2012

  • 103015 Condensed matter
  • 103017 Magnetism
  • 103029 Statistical physics

Keywords

  • WEAK FERROMAGNETISM
  • CRYSTALS
  • STATES

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