Enhanced skyrmion metastability under applied strain in FeGe

TL;DR

This study demonstrates that applying strain to FeGe enhances the metastability of skyrmions, allowing them to persist at lower temperatures and after magnetic field reversal, which could improve skyrmion-based applications.

Contribution

The paper reveals how thermal strain influences skyrmion metastability in FeGe, showing that strain application significantly extends skyrmion lifetime and stability.

Findings

Strain along [110] stabilizes metastable skyrmions at low temperatures.

Metastable skyrmions persist after magnetic field reversal under strain.

Strain increases the energy barrier protecting skyrmions from decay.

Abstract

Mechanical straining of skyrmion hosting materials has previously demonstrated increased phase stability through the expansion of the skyrmion equilibrium pocket. Additionally, metastable skyrmions can be generated via rapid field-cooling to form significant skyrmion populations at low temperatures. Using small-angle x-ray scattering and x-ray holographic imaging on a thermally strained 200 nm thick FeGe lamella, we observe temperature-induced strain effects on the structure and metastability of the skyrmion lattice. We find that in this sample orientation (H || [1 1 0]) with no strain, metastable skyrmions produced by field cooling through the equilibrium skyrmion pocket vanish from the sample upon dropping below the well known helical reorientation temperature. However, when strain is applied along [110] axis, and this procedure is repeated, a substantial volume fraction of metastable skyrmions persist upon cooling below this temperature down to 100 K. Additionally, we observe a large number of skyrmions retained after a complete magnetic field polarity reversal, implying that the metastable energy barrier protecting skyrmions from decay is enhanced.