Speaker
Description
Bloch points are three-dimensional singularities in magnetization that play a key role in topological transformations of spin textures. Using a geometrical approach, here we demonstrate deterministic control of the internal magnetic structure of Bloch point. This is achieved by creating a chirality interface between two three-dimensional double-helix nanowires of opposite helicity, which form a kinked, non-collinear structure. A saturating magnetic field nucleates head-to-head or tail-to-tail configurations at the chirality interface, leading to the formation of a Bloch point in the vicinity of the chirality interface.
Combining advanced experimental tomography techniques, including transmission electron microscopy (TEM) and x-ray magnetic circular dichroism (XMCD), with micromagnetic simulations, we confirm that domain walls containing circulating Bloch points are reliably nucleated with predefined polarity and circulation. These Bloch points also have a hyperbolic character, with a helicity angle ≠90°. Due to the combination of tailored geometry and the robustness of the initialization field protocol, our approach thus facilitates future 3D spintronic device architectures containing Bloch points with controlled properties.