Picosecond localization dynamics following ultrafast nanoscale magnetic switching

TL;DR

This study investigates how ultrafast laser pulses induce nanometer-scale magnetic domain nucleation and localization, revealing that localization occurs rapidly and is influenced by the magnetic landscape, differing from traditional phase transitions.

Contribution

It demonstrates real-time tracking of spin texture nucleation and localization, showing that these are distinct processes and that localization can be controlled through landscape tailoring.

Findings

Localization occurs in less than one nanosecond.

Nucleation is homogeneous via fluctuations.

Localization is governed by variations in spin-texture lifetimes.

Abstract

Ultrashort laser pulses provide the fastest known way to switch magnetic order. Such excitation commonly creates nanometer-scale domains, even after homogeneous illumination when the position of nucleated domains is not externally defined. However, the physics of domain localization during such ultrafast phase transitions remains unresolved. Here, we use shot-resolved pump-probe resonant x-ray scattering together with a material featuring a periodically modulated magnetic anisotropy landscape to track, in real time, the laser-driven nucleation and localization of nanometer-scale spin textures. We find that nucleation and localization are two distinct processes. Nucleation occurs homogeneously via fluctuations at early times, whereas spatially periodic structures emerge only later and, under suitable conditions, localize in less than one nanosecond. Real-space simulations show that this localization is governed by strong lateral variations in spin-texture lifetimes. Our results demonstrate that ultrafast phase-transition dynamics fundamentally differ from conventional transitions, yet still can be controlled through moderate nanometer-scale tailoring of the energy landscape.