Soliton motion in skyrmion chains: Stabilization and guidance by nanoengineered pinning

Abstract

Using a particle-based model we examine the depinning motion of solitons in skyrmion chains in quasi-one dimensional (1D) and two-dimensional (2D) systems containing embedded 1D interfaces. The solitons take the form of a particle or hole in a commensurate chain of skyrmions. Under an applied drive, just above a critical depinning threshold the soliton moves with a skyrmion Hall angle of zero. For higher drives, the entire chain depins, and in a 2D system we observe that both the solitons and chain move at zero skyrmion Hall angle and then transition to a finite skyrmion Hall angle as the drive increases. In a 2D system with a 1D interface that is at an angle to the driving direction, there can be a reversal of the sign of the skyrmion Hall angle from positive to negative. Our results suggest that solitons in skyrmion systems could be used as information carriers in racetrack geometries that would avoid the drawbacks of finite skyrmion Hall angles. The soliton states become mobile at significantly lower drives than the depinning transition of the skyrmion chains themselves.

Dynamics of orbital skyrmions in a circular nanodisk

“…We show that the in situ tunability of the skyrmion oscillation could be achieved, i.e., for a lower subthreshold J, at which the OSs perform the CW or CCW circular motion in one orbit of the proposed nanodisk, whereas at a higher suprathreshold J, the OSs can switch into the other orbit. The co-oscillation of two OSs is also demonstrated in the proposed nanodisk, which could be used as a multifrequency generator with enhanced maximum f. Our results give insights into the OS dynamics and may trigger further studies on collective effects 38,39 of a group of skyrmions or other magnetic quasiparticles in a single disk…”

“…The co-oscillation of two OSs is also demonstrated in the proposed nanodisk, which could be used as a multifrequency generator with enhanced maximum f . Our results give insights into the OS dynamics and may trigger further studies on collective effects 38,39 of a group of skyrmions or other magnetic quasiparticles in a single disk or coupled disks, 40 providing more possibilities for skyrmion manipulation for future spintronic applications.…”

Spontaneous skyrmion conformal lattice and transverse motion during dc and ac compression

“…In order to better understand the role of the changing size of the skyrmions, we have also considered a Thiele equation approach in which the skyrmions are treated as point-like particles that have a repulsive interaction with each other and move under damping and a Magnus term [17], similar to what has been employed in previous studies [24][25][26]. The equation of motion for a skyrmion i is…”

“…There is increasing interest in identifying ways to control individual and collective skyrmion motion. Possible methods include periodic pinning [21][22][23][24][25][26], ratchet effects [27][28][29][30][31][32], interface guided motion [33,34], strain, magnetic or temperature gradients [35][36][37][38], one-dimensional potential wells [39], curvature of the sample [40][41][42], and skyrmion-vortex coupling using a ferromagnet-superconductor heterostructure [43]. Skyrmions can also be manipulated by being compressed against a wall or linear obstacle, such as by applying a drive that forces the skyrmions to move toward an interface or extended nanostructure.…”

Skyrmion transport and annihilation in funnel geometries

“…From a technological application point of view, a finite skyrmion Hall angle is problematic because it can cause the skyrmion to deviate towards the sample edge and annihilate, destroying any information that may have been associated with the skyrmion location. There have been various efforts to understand how to control the skyrmion motion and mitigate the intrinsic Hall angle, including through the use of periodic pinning [18][19][20][21], ratchet effects [22][23][24][25], 1D potential wells [26][27][28][29][30], nanotracks [31,32], soliton motion [33], interface guided motion [34] and gradients in the strain, temperature, or magnetic field [35][36][37][38].…”