Role of gallium diffusion in the formation of a magnetically dead layer at the Y3Fe5O12/Gd3Ga5O12 epitaxial interface

S M Suturin,V E Bursian,A Vorobiev,A M Korovin,L V Lutsev,N L Yakovlev,L Pasquali,V Ukleev,V Bourobina,A Devishvili,M Montecchi,N S Sokolov

doi:10.1103/physrevmaterials.2.104404

Abstract

We have clarified the origin of magnetically dead interface layer formed in yttrium iron garnet (YIG) films grown at above 700{\deg}C onto gadolinium gallium garnet (GGG) substrate by means of laser molecular beam epitaxy. The diffusion-assisted formation of a Ga-rich region at the YIG / GGG interface is demonstrated by means of composition depth profiling performed by X-ray photoelectron spectroscopy, secondary ion mass spectroscopy and X-ray and neutron reflectometry. Our finding is in sharp contrast to the earlier expressed assumption that Gd acts as a migrant element in the YIG/GGG system. We further correlate the presence of Ga-rich transition layer with considerable quenching of ferromagnetic resonance and spin wave propagation in thin YIG films. Finally, we clarify the origin of the enigmatic low-density overlayer that is often observed in neutron and X-ray reflectometry studies of the YIG / GGG epitaxial system.

Highlights

The intense interest in nanometer-scale epitaxial films of yttrium iron garnet (Y3Fe5O12, YIG) is supported by potential applications in magnonic devices [1,2,3], exploiting the idea of data transfer via spin waves (SWs) [4]
We directly show this effect in thin YIG films by means of the ferromagnetic resonance, spin wave propagation, and polarized neutron reflectometry
We have demonstrated that the resonance magnetic properties are noticeably quenched as the YIG film thickness decreases to a value of few nanometers

Summary

INTRODUCTION

The intense interest in nanometer-scale epitaxial films of yttrium iron garnet (Y3Fe5O12, YIG) is supported by potential applications in magnonic devices [1,2,3], exploiting the idea of data transfer via spin waves (SWs) [4]. Due to the absence of threemagnon scattering [5], the spin wave damping is expected to be significantly lower in YIG ultrathin films with thickness ranging from a few nanometers to a few tens of nanometers. In the present work we investigated in detail the YIG/GGG epitaxial layers grown at 700–1000 °C by laser MBE, paying particular attention to the properties of the interface region. We demonstrate drastic quenching of ferromagnetic resonance and spin wave propagation in ultrathin YIG films, correlating it to the structural data obtained by composition depth profiling. The presented results are specific for YIG layers grown by laser MBE and do not necessarily apply to the other growth techniques such as liquid phase epitaxy

EXPERIMENT

COMPOSITION AND MAGNETIZATION IN-DEPTH PROFILING BY PNR AND XRR

CONCLUSION

Findings

Methods