The Dzyaloshinskii-Moriya interaction (DMI) in magnetic systems stabilizes spin textures with preferred chirality, applicable to next-generation memory and computing architectures. In perpendicularly magnetized heavy-metal/ferromagnet films, the interfacial DMI originating from structural inversion asymmetry and strong spin-orbit coupling favors chiral N\'eel-type domain walls (DWs) whose energetics and mobility remain at issue. Here, we characterize a new effect in which domains expand unidirectionally in response to a combination of out-of-plane and in-plane magnetic fields, with the growth direction controlled by the in-plane field strength. These growth directionalities and symmetries with applied fields cannot be understood from static treatments alone. We theoretically demonstrate that perpendicular field torques stabilize steady-state magnetization profiles highly asymmetric in elastic energy, resulting in a dynamic symmetry breaking consistent with the experimental findings. This phenomenon sheds light on the mechanisms governing the dynamics of N\'eel-type DWs and expands the utility of field-driven DW motion to probe and control chiral DWs.
@article{arxiv.2102.07909,
title = {Dynamic symmetry breaking in chiral magnetic systems},
author = {Jeffrey A. Brock and Michael D. Kitcher and Pierre Vallobra and Rajasekhar Medapalli and Maxwell P. Li and Marc De Graef and Stéphane Mangin and Vincent Sokalski and Eric E. Fullerton},
journal= {arXiv preprint arXiv:2102.07909},
year = {2021}
}