Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5-10 GHz frequency range

TL;DR

This paper introduces a novel microwave synchronized x-ray microscopy technique capable of imaging nanoscale magnetization dynamics at 5-10 GHz with 35 nm resolution, enabling detailed studies of high-frequency magnetic phenomena.

Contribution

The authors developed a new microscopy setup combining microwave synchronization with single photon counting, achieving high sensitivity and stability for imaging magnetization dynamics at synchrotron sources.

Findings

Imaging of a 6 GHz nanoscale spin wave generated by a spin torque oscillator.

Observation of uniform ferromagnetic precession at 9 GHz with ~0.1 deg amplitude.

Demonstration of direct, phase-resolved images of high-frequency magnetic phenomena.

Abstract

We present a scanning transmission x-ray microscopy setup combined with a novel microwave synchronization scheme in order to study high frequency magnetization dynamics at synchrotron light sources. The sensitivity necessary to detect small changes of the magnetization on short time scales and nanometer spatial dimensions is achieved by combination of the developed excitation mechanism with a single photon counting electronics that is locked to the synchrotron operation frequency. The required mechanical stability is achieved by a compact design of the microscope. Our instrument is capable of creating direct images of dynamical phenomena in the 5-10 GHz range, with 35 nm resolution. When used together with circularly polarized x-rays, the above capabilities can be combined to study magnetic phenomena at microwave frequencies, such as ferromagnetic resonance (FMR) and spin waves. We demonstrate the capabilities of our technique by presenting phase resolved images of a 6 GHz nanoscale spin wave generated by a spin torque oscillator, as well as the uniform ferromagnetic precession with ~0.1 deg amplitude at 9 GHz in a micrometer-sized cobalt strip.