Antiferromagnetic Skyrmion Scattering Revealed by Direct Time-Resolved Imaging of Collective Dynamics

TL;DR

This study visualizes and quantifies the real-time collective dynamics and scattering interactions of antiferromagnetic skyrmions, revealing regimes of incoherent and coherent flow, and providing insights for spintronic device development.

Contribution

It introduces a direct imaging method to analyze AFM skyrmion interactions, quantifies the scattering potential, and demonstrates controlled collective dynamics for potential device applications.

Findings

Revealed two flow regimes: incoherent scattering and coherent translation.

Quantified the skyrmion-skyrmion scattering potential as exponentially decaying with 30 nm range.

Achieved GHz operation with robust, deformation-free collective motion at high current densities.

Abstract

Scattering analysis offers a fundamental route to revealing particle interactions with direct implications for device technologies relying on ensembles of particles such as magnetic skyrmions. Here, we directly visualize, in real time, the nanosecond current-driven dynamics of an antiferromagnetic (AFM) skyrmion lattice using element-specific pump-probe X-ray microscopy. By tuning spin-orbit torque relative to local pinning potentials, we reveal two regimes: incoherent flow, where mobile skyrmions scatter from pinned ones, inducing recoil dynamics with 3-20 ns relaxation, and coherent flow, where the lattice translates uniformly. Quantification of the reproducible post-pulse relaxation trajectories via an inverse analyis method based on the Thiele equation yields the nanoscale AFM skyrmion-skyrmion scattering potential, which decays exponentially with a range of 30 nm, in full agreement with micromagnetic simulations. At higher current densities, the lattice exhibits coherent motion free from detectable Hall and inertial effects or dynamical deformation, enabling robust GHz operation. These findings establish a quantitative framework for AFM skyrmion interactions and demonstrate deterministic control of their collective dynamics over billions of cycles even in the incoherent flow regime, thereby paving the way for multi-skyrmion spintronic devices.