Ultrafast depinning of domain walls in notched antiferromagnetic nanostructures

The pinning/depinning of an antiferromagnetic (AFM) domain wall is certainly the core issue for AFM spintronic device operation. In this work, we study theoretically the N\'eel-type domain wall pinning/depinning at a notch in an AFM nanostructure (nanoribbon). The depinning field depending on the notch dimension and intrinsic material properties is deduced and also numerically calculated. Contrary to conventional conception, it is revealed that the depinning field is remarkably dependent on the damping constant and the time-dependent oscillation of domain wall position in the weakly damping regime benefits to the wall depinning, resulting in a gradual saturation of the depinning field with increasing damping constant. A one-dimensional model accounting of the internal dynamics of the domain wall is used to explain perfectly the simulated results. It is demonstrated that the depinning mechanism of an AFM domain wall differs from the ferromagnetic domain wall by exhibiting a depinning typically three orders of magnitude faster than the latter, unveiling another origin for ultrafast dynamics of an AFM system.