Spin Seebeck effect at microwave frequencies

TL;DR

This study investigates the frequency response of the spin Seebeck effect in yttrium iron garnet/platinum bilayers, revealing a thickness-dependent cutoff frequency up to 350 MHz, which informs the control of spin current emission.

Contribution

It demonstrates how the magnon spectrum and spin current emission in the spin Seebeck effect can be tuned by varying the ferromagnetic layer thickness.

Findings

Cutoff frequency up to 350 MHz in 50 nm thick films

Cutoff frequency drops below 1 MHz in micrometer-thick films

Magnon spectrum shaping depends on ferromagnetic layer thickness

Abstract

We experimentally study the transient voltage response of yttrium iron garnet/platinum bilayer samples subject to periodic heating up to gigahertz frequencies. We observe an intrinsic cutoff frequency of the induced thermopower voltage, which characteristically depends on the thickness of the yttrium iron garnet film. The cutoff frequency reaches values of up to 350 MHz in a 50 nm thick yttrium iron garnet film, but drops to below 1 MHz for several-micrometer-thick films. These data corroborate the notion that the magnon spectrum responsible for the spin current emission in the spin Seebeck effect can be shaped by tuning the thickness of the ferromagnetic layer.