Direct Imaging of current Induced Vortex Domain Wall Dynamics

STXMRing

Domain walls are emergent magnetic quasi-particles that exhibit a range of fascinating properties such as an effective mass, inertia and automotion without external fields. These quasi-particles can be studied particularly effectively in a ring geometry where the position of a wall can be engineered by external fields and the geometry [1].

Controlling the dynamics of a ferromagnetic domain wall on a local scale is a key prerequisite for precise manipulation and reproducible spin switching by domain wall motion [2]. We investigate the local control of the domain wall velocity by tailoring the domain wall potential landscape via local variations of the ring geometry [3]. Employing time-resolved scanning transmission X-ray microscopy (STXM), we dynamically image the motion of domain walls in rotating magnetic fields and quantify the contribution of the spatially varying potential to the domain wall dynamics. The interplay of these forces leads to distortion-free wall motion and the engineered domain wall potential landscape is used for spatial synchronization of domain wall velocities in ferromagnetic rings. These attributes are both key prerequisites for the implementation of domain wall-based devices [4]. We determine the dynamics of the domain wall nucleation as well as the automotion that are both governed by the tailored geometry [5].

[1] M. Kläui, Topical Review in Journal of Physics: Condensed Matter 20, 313001 (2008).
[2] A. Bisig, et al., Nature Communications 4, 2328 (2013).
[3] K. Richter, et al, Physical Review Applied 5, 024007 (2016).
[4] J.-G. Zhu, et al., Journal of Applied Physics 87, 6668 (2000).
[5] K. Richter et al., Phys. Rev. B 94, 024435 (2016).