Chirality of domain wall mobility in different regimes of domain wall propagation in epitaxial Pd/Co/Pd(111) films

The dynamics of domain walls (DWs) was systematically investigated in epitaxial Pd/Co/Pd(111) samples with different thicknesses of the Pd bottom layer and, as a consequence, different interface roughnesses in the creep and flow regimes. The DWs were displaced by the simultaneous action of driving out-of-plane (OOP) and symmetry-breaking in-plane (IP) magnetic fields. A pronounced asymmetry in the dependencies of the velocities of the DWs on the applied IP magnetic field, $v({H}_{x})$, was observed in the creep regime, which was related to the dependence of the mobility of the DWs on their chirality, presumably due to a chiral damping. The investigated samples revealed different depinning fields due to different interface roughnesses. Notably, the asymmetry in the $v({H}_{x})$ dependencies almost disappeared in the flow regime, regardless of the extent of asymmetry observed in the creep regime and the values of depinning fields in the samples. We explain this fact by the precessional dynamics of DWs in the flow regime, in which the chirality of DWs changes between left-handed to right-handed with a large frequency, thus making DWs achiral on average. This study would deepen the understanding of the chiral dynamics of DWs and advance the development of DW devices.