Pump--probe x-ray microscopy of photo-induced magnetization dynamics at MHz repetition rates

TL;DR

This study demonstrates high-repetition-rate pump-probe x-ray microscopy capable of imaging nanometer-scale, picosecond to nanosecond magnetization dynamics in thin magnetic films, enabling destruction-free, high-resolution analysis of photo-induced magnetic processes.

Contribution

The paper introduces a novel time-resolved x-ray microscopy technique operating at 50 MHz, allowing detailed imaging of ultrafast magnetization dynamics with nanometer spatial resolution.

Findings

Imaging of laser-induced demagnetization and remagnetization on nanosecond timescales.

Achievement of destruction-free measurements at 50 MHz repetition rate.

Observation of lateral heterogeneity in magnetization dynamics due to near-field effects.

Abstract

We present time-resolved scanning x-ray microscopy measurements with picosecond photo-excitation via a tailored infrared pump laser at a scanning transmission x-ray microscope. Specifically, we image the laser-induced demagnetization and remagnetization of thin ferrimagnetic GdFe films proceeding on a few nanoseconds time scale. Controlling the heat load on the sample via additional reflector and heat-sink layers allows us to conduct destruction-free measurements at a repetition rate of \SI{50}{\mega\hertz}. Near-field enhancement of the photo-excitation and controlled annealing effects lead to laterally heterogeneous magnetization dynamics which we trace with \SI{30}{\nano\meter} spatial resolution. Our work opens new opportunities to study photo-induced dynamics on the nanometer scale, with access to picosecond to nanosecond timescales, which is of technological relevance, especially in the field of magnetism.