Free-standing and positionable microwave antenna device for magneto-optical spectroscopy experiments

TL;DR

This paper introduces a detachable, positionable microwave antenna device on a flexible glass substrate, enabling advanced magnetization spectroscopy techniques without complex fabrication on each sample.

Contribution

The authors present a novel, flexible, and detachable microwave antenna platform that simplifies magnetization excitation in spectroscopy experiments, compatible with optical and non-optical methods.

Findings

Achieved a 400-fold enhancement in magnon signal using the antenna.

Demonstrated spatial resolution in yttrium iron garnet thin films.

Validated the antenna's effectiveness in optical ferromagnetic resonance experiments.

Abstract

Modern spectroscopic techniques for the investigation of magnetization dynamics in micro- and nano- structures or thin films use typically microwave antennas which are directly fabricated on top of the sample by means of electron-beam-lithography (EBL). Following this approach, every magnetic structure on the sample needs its own antenna, resulting in additional EBL steps and layer deposition processes. We demonstrate a new approach for magnetization excitation that is suitable for optical and non-optical spectroscopy techniques. By patterning the antenna on a separated flexible glass cantilever and insulating it electrically, we solved the before mentioned issues. Since we use flexible transparent glass as a substrate, optical spectroscopy techniques like Brillouin-light-scattering microscopy ({\mu}BLS), time resolved magneto-optical Kerr effect measurements (TRMOKE) or optical detected magnetic resonance (ODMR) measurements can be carried out at visible laser wavelengths. As the antenna is detached from the sample it can be freely positioned in all three dimensions to adress only the desired magnetic sample structures and to achieve effective excitation. We demonstrate the functionality of these antennas using {\mu}BLS and compare coherently and thermally excited magnon spectra to show the enhancement of the signal by a factor of about 400 due to the excitation by the antenna. Moreover, we succeed to characterize yttrium iron garnet thin films with spatial resolution using optical ferromagnetic resonance (FMR) experiments. We analyse the spatial excitation profile of the antenna by measuring the magnetization dynamics in two dimensions. The technique is furthermore applied to investigate injection-locking of spin Hall nano-oscillators.