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Three different geometries after the domain wall nucleation process with 150 Oe magnetic field component in the sample plane perpendicular to the wires (indicated by the arrow). Tail-to-tail (t2t) domain walls are seen at the -shaped bend and head-to-head (h2h) walls at -bend. Schematic drawings visualize the approximate spin structure of the walls (note that the arrows represent the average magnetization in a large area). In geometry 1, a transverse domain wall is seen at the left kink and a vortex domain wall with clockwise (cw) chirality one further to the right. In geometry 2 all vortex walls have ccw chirality. The topological edge defects of a vortex domain wall, that are connected by a diagonal line, are indicated by arrows in the sketch of the left wall. There are two cw vortex domain walls in geometry 3. In all wires a white end domain wall is visible at the left and a black end domain wall at the right end.
After reversal of the nucleation field compared to Fig. 1: Initial h2h domain walls at the bends, black end domain walls at the left end [(a) and (c)] and white end domain walls at the right end [(e) and (g)]. Left end: (a) cw vortex wall, after a field pulse of 31 Oe forms end vortex wall with same chirality (b). (c) ccw vortex wall that transforms to cw end vortex wall after a field pulse of 6 Oe (d). Right end: (e) cw vortex domain wall transforms to ccw end vortex wall (f) after a field pulse of 7 Oe. The ccw wall (g) however does not transform after a field pulse of 11 Oe (h).
Two different wires with one bend (width 500 nm thickness 20 nm). (a) Wire 1: t2t cw vortex domain wall after nucleation as in Fig. 1. (b) After a magnetic field pulse of 16 Oe an end vortex is formed with opposite (ccw) chirality, the magnetizations points to the right. (c) The end vortex is depinned with a field pulse of 55 Oe and the magnetization switches, the vortex leaves the wire at the right end. (d) Wire 2: t2t cw vortex domain wall after nucleation. (e) Vortex wall moved to the right end and without chirality transformation after a field pulse of 20 Oe. (f) The magnetization switches after a field pulse of 70 Oe while the vortex end domain is still pinned. The end domain at the left end changes from “\” to “/” shape. (g) The vortex end domain is depinned at 70 Oe and moves to the left. The chirality transforms to ccw. (h) The end vortex domain is depinned at the left end and leaves the wire at the right after a field pulse of 70 Oe.
(a) Initial cw wall: The magnetic moments in A and B lie in almost the same direction. Under a field pulse the moments in between can rotate continuously and (b) no chirality transformation visible. (c) Initial ccw wall: The magnetic moments in A and B lie almost antiparallel, the vortex core is expelled in D and a new vortex core is nucleated in C resulting in (b) a cw end vortex domain. [(e)–(h)] Results of micromagnetic simulation (Ref. 20) (width 500 nm, 20 nm thickness, length, 5 nm cell size, exchange constant , damping constant , and the saturation magnetization ). (d) Initial state. (e) Magnetic field of 24 Oe applied, the left half of the vortex wall interacts with the end domain, while the vortex core moves toward the bottom edge of the wire. (f) A new vortex core is nucleated in the area where both walls meet (between blue and yellow). (g) The old vortex core is pushed further to the bottom edge and it is more or less separated from the end vortex domain. (h) Final result which is the same as in our experiments.
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