Direct observation of coherent magnons with suboptical wavelengths in a single-crystalline ferrimagnetic insulator

J Förster,S Mayr,O Surzhenko,S Finizio,M Weigand,F Groß,J Bailey,H Stoll,G Schütz,N Träger,J Raabe,J Gräfe,S Wintz,C Dubs,N Liebing,G Woltersdorf

doi:10.1103/physrevb.100.214416

Abstract

In the field of magnetism, spin waves are a subject of great interest for fundamental and application-oriented research. Time-resolved scanning transmission x-ray microscopy, a technique that allows for direct spin-wave imaging below the optical resolution limit, is usually limited to thin layers deposited on x-ray transparent membranes. Here, the authors report on a preparation routine that makes single-crystalline materials accessible to this powerful technique. The latter is subsequently implemented on the ferrimagnetic insulator yttrium iron garnet, where spin waves down to 100-nm wavelength are observed.

Highlights

Spin waves are the fundamental excitations of ordered spin systems with the magnon being their quasiparticle of excitation
Image (b) features a frame of the corresponding dynamic movie recorded for an excitation frequency of f = 2.5 GHz and an external magnetic field of μ0Hext = 18 mT
This work demonstrates the application of time-resolved STXM for the imaging of spin dynamics in extended singlecrystalline yttrium iron garnet (YIG) thin films

Summary

Introduction

Spin waves are the fundamental excitations of ordered spin systems with the magnon being their quasiparticle of excitation. For almost 100 years, spin waves have been an active topic in magnetism research [1,2,3,4] During this time, the ferrimagnetic insulator yttrium iron garnet (YIG) has stood out as platform for experimental studies on spin waves [3,4,5,6]. The ferrimagnetic insulator yttrium iron garnet (YIG) has stood out as platform for experimental studies on spin waves [3,4,5,6] The reason for this lies in its exceptionally low intrinsic magnetic damping, which leads to very high spin-wave lifetimes and propagation lengths [7]. Combined with advances in optical spin wave measurement techniques like Brillouin light scattering (BLS) [7,8,11,12], and time-resolved Kerr effect microscopy (TR-MOKE) [13,14], as well as all-electrical spin-wave spectroscopy [6,15,16], this has lead to extensive studies of spin waves in various magnetic systems, in particular in thin magnetic films

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Conclusion