Ultrafast high-harmonic nanoscopy of magnetization dynamics

Sergey Zayko,Murat Sivis,Claus Ropers,Michael Heigl,Michael Lohmann,Ofer Kfir,Manfred Albrecht

doi:10.1038/s41467-021-26594-0

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 timescales 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 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 compact experimental setup demonstrates the highest spatio-temporal resolution of magneto-optical imaging to date. Facilitating ultrafast imaging with high sensitivity to chiral and linear dichroism, we envisage a wide range of applications spanning magnetism, phase transitions, and carrier dynamics.

Highlights

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
Time-resolved measurement schemes were developed to access magnetic dynamics with sub-100 nm spatial and picosecond temporal resolutions. These are based on established imaging techniques, such as spin-polarized scanning tunneling microscopy[22], Lorentz-contrast electron microscopy[23,24,25,26,27,28,29], scanning transmission x-ray microscopy[30,31], high-resolution ptychography[32,33] and tomography[34,35], as well as full-field magneto-optical imaging approaches including Fourier transform holography (FTH)[31,36,37,38] and coherent diffractive imaging (CDI)[39,40]
We introduce ultrafast dichroic nanoscopy based on high-harmonic radiation, reaching unprecedented spatiotemporal resolution in full-field magneto-optical imaging

Summary

Introduction

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. Time-resolved measurement schemes were developed to access magnetic dynamics with sub-100 nm spatial and picosecond temporal resolutions. We introduce ultrafast dichroic nanoscopy based on high-harmonic radiation, reaching unprecedented spatiotemporal resolution in full-field magneto-optical imaging.

Results

Conclusion