Spin transport in an insulating ferrimagnetic-antiferromagnetic-ferrimagnetic trilayer as a function of temperature

TL;DR

This study investigates how thermally generated spin currents behave in an insulating ferrimagnetic-antiferromagnetic-ferrimagnetic trilayer across various temperatures, revealing key insights into spin transport mechanisms and substrate effects.

Contribution

It provides the first detailed analysis of spin Seebeck effect in a YIG/NiO/YIG trilayer over a wide temperature range, highlighting the role of NiO thickness and substrate influence.

Findings

NiO spin diffusion length is 4.2 nm at room temperature.

Inverse spin Hall signals are influenced by the GGG substrate below 30 K.

A peak in SSE response around 100 K indicates increased spin diffusion in YIG.

Abstract

We present a study of the transport properties of thermally generated spin currents in an insulating ferrimagnetic-antiferromagnetic-ferrimagnetic trilayer over a wide range of temperature. Spin currents generated by the spin Seebeck effect (SSE) in a yttrium iron garnet (YIG) YIG/NiO/YIG trilayer on a gadolinium gallium garnet (GGG) substrate were detected using the inverse spin Hall effect in Pt. By studying samples with different NiO thicknesses, the NiO spin diffusion length was determined to be 4.2 nm at room temperature. Interestingly, below 30 K, the inverse spin Hall signals are associated with the GGG substrate. The field dependence of the signal follows a Brillouin function for a S=7/2 spin ($\mathrm{Gd^{3+}}$) at low temperature. Sharp changes in the SSE signal at low fields are due to switching of the YIG magnetization. A broad peak in the SSE response was observed around 100 K, which we associate with an increase in the spin-diffusion length in YIG. These observations are important in understanding the generation and transport properties of spin currents through magnetic insulators and the role of a paramagnetic substrate in spin current generation.