Chiral surface twists and skyrmion stability in nanolayers of cubic helimagnets

Lorentz transmission electron microscopy (LTEM) investigations of modulated states in a FeGe wedge and detailed calculations demonstrate that chiral twists arising near the surfaces of noncentrosymmetric ferromagnets (Meynell et al. Phys. Rev. B, 90, 014406 (2014)) provide a stabilization mechanism for skyrmion lattices and helicoids in cubic helimagnet nanolayers. The calculated magnetic phase diagram for free standing cubic helimagnet nanolayers shows that magnetization processes in these compounds fundamentally differ from those in bulk cubic helimagnets and are characterized by the first-order transitions between modulated phases and the formation of specific multidomain states. The paper reports LTEM observations of multidomain patterns in FeGe free-standing nanolayers.