Ultrafast high-harmonic nanoscopy of magnetization dynamics

TL;DR

This paper introduces a novel ultrafast high-harmonic nanoscopy technique that enables real-space imaging of femtosecond magnetization dynamics with nanometer spatial resolution, revealing nanoscale spin texture evolution.

Contribution

It demonstrates the first high-spatial and temporal resolution magnetic imaging method using circularly polarized high-harmonic radiation for femtosecond magnetization studies.

Findings

Mapped magnetic domains with 16 nm resolution

Tracked spin dynamics with 40 fs temporal resolution

Observed reversible and irreversible magnetic texture changes

Abstract

Light-induced magnetization changes, such as all-optical switching, skyrmion nucleation, and intersite spin transfer, unfold on temporal and spatial scales down to femtoseconds and nanometers, respectively. Pump-probe spectroscopy and diffraction studies indicate that spatio-temporal dynamics may drastically affect the non-equilibrium magnetic evolution. Yet, direct real-space magnetic imaging on the relevant timescale has remained challenging. Here, we demonstrate ultrafast high-harmonic nanoscopy employing circularly polarized high-harmonic radiation for real-space imaging of femtosecond magnetization dynamics. We observe the reversible and irreversible evolution of nanoscale spin textures following femtosecond laser excitation. Specifically, we map quenched magnetic domains and localized spin structures in Co/Pd multilayers with a sub-wavelength spatial resolution down to 16 nm, and strobosocopically trace the local magnetization dynamics with 40 fs temporal resolution. Our approach enables the highest spatio-temporal resolution of magneto-optical imaging to date. Facilitating ultrafast imaging with an extreme sensitivity to various microscopic degrees of freedom expressed in chiral and linear dichroism, we envisage a wide range of applications spanning magnetism, phase transitions, and carrier dynamics.