High-Frequency Dynamics and Electrical Signatures of a 3D Bloch Point.

Three-dimensional topological magnetic defects, such as Bloch points, are of significant interest for high-frequency spintronics due to their unique particle-like properties and effective inertial mass. We investigate the nucleation, stabilization, and driven dynamics of an isolated Bloch point in a ferromagnetic multilayer with alternating in-plane and perpendicular magnetic anisotropy. Using micromagnetic simulations, we show that a perpendicular magnetic field stabilizes a head-to-head Bloch point state, while a transient in-plane field pulse drives the defect into gyrotropic and nutation motion. To model the dynamics, we develop a collective-coordinate Lagrangian description of the Bloch point core. We further demonstrate that the time-dependent core displacement generates a transverse charge current via spin pumping and inherent spin-to-charge conversion within the multilayer system. The resulting current spectrum contains low-frequency and high-frequency components, including an intrinsic nutation mode in the gigahertz range. Our findings expand the capabilities for electrical control and identification of complex spin configurations, contributing to the development of active three-dimensional spintronic devices.