Enhancement of the spin Seebeck effect owing to bismuth substitution in thermoelectric generators fabricated from LPE Bi-substituted YIG films

Masaaki Imamura,Jiro Kitagawa,Daisuke Tashima,Ryo Nishimura,Keita Yamaguchi,Hironori Asada

doi:10.1063/9.0000042

Masaaki Imamura, Jiro Kitagawa + Show 4 more

Open Access

https://doi.org/10.1063/9.0000042

Copy DOI

Abstract

Raising the thermoelectric voltage in spin thermoelectric generators is an important subject. We investigated the substitution of bismuth for yttrium to increase spin pumping at the paramagnetic metal and ferrimagnetic insulator (PM/FMI) interface, and tested bismuth-substituted iron garnet films grown by liquid phase epitaxy. Epitaxial Bi-substituted iron garnet films exhibit large growth-induced magnetic anisotropy perpendicular to the film surface. This anisotropy increases the magnetic damping α in the FMI; α also increases with increasing Bi content. We report the rise in voltage observed in a spin thermoelectric generator incorporating Bi-substituted YIG films grown by liquid phase epitaxy, and explain the origin of the voltage rise based on the results of FMR measurements.

Highlights

A spin-thermoelectric (STE) generator is composed of a thin paramagnetic metal (PM) layer, a ferrimagnetic insulator (FMI) and a paramagnetic metal and ferrimagnetic insulator (PM/FMI) bilayer interface
It has been reported that bismuth-substituted iron garnet (Bi:YIG) films grown by liquid phase epitaxy (LPE) on gadolinium gallium garnet (GGG) substrates exhibit a large growth-induced anisotropy perpendicular to the film surface
We conclude that larger spin currents were generated in the LPE Bi-substituted YIG films, which exhibit large growth-induced magnetic anisotropy, and increased values of VSTE were observed in STE generators incorporating LPE Bi:YIG films

Summary

INTRODUCTION

A spin-thermoelectric (STE) generator is composed of a thin paramagnetic metal (PM) layer, a ferrimagnetic insulator (FMI) and a PM/FMI bilayer interface. It has been reported that bismuth-substituted iron garnet (Bi:YIG) films grown by liquid phase epitaxy (LPE) on gadolinium gallium garnet (GGG) substrates exhibit a large growth-induced anisotropy perpendicular to the film surface.. It has been reported that bismuth-substituted iron garnet (Bi:YIG) films grown by liquid phase epitaxy (LPE) on gadolinium gallium garnet (GGG) substrates exhibit a large growth-induced anisotropy perpendicular to the film surface.12 The damping process occurs through energy dissipation by spin-orbit coupling (SOC). As a modern concept in STE generation, the effect of spin-orbit interactions (SOI) on free s-electron spins in the PM layer is used to explain the inverse spin Hall effect (ISHE), here we consider the SOC of local d-electron spins that is known as Russell-Saunders coupling, and study its effects on spin-thermoelectric phenomena

CRYSTALLINITY AND SOC OF LPE Bi:YIG FILMS

GROWTH-INDUCED MAGNETIC ANISOTROPY OF LPE Bi:YIG FILMS

FMR CHARACTERISTICS OF LPE Bi:YIG FILMS

SPIN THERMOELECTRIC VOLTAGE

Findings

CONCLUSION