Transient response of spin Peltier effect revealed by lock-in thermoreflectance measurement

TL;DR

This study investigates the transient behavior of the spin Peltier effect using high-frequency lock-in thermoreflectance, revealing a frequency-dependent decrease in temperature modulation and estimating the effect's length scale.

Contribution

It introduces a high-frequency measurement approach to study the spin Peltier effect's transient response and estimates its characteristic length scale, advancing understanding of its dynamics.

Findings

SPE-induced temperature modulation decreases above 1 kHz.

The length scale of SPE is approximately 0.94 micrometers.

High-frequency measurements reveal dynamics not seen in low-frequency studies.

Abstract

Transient response of the spin Peltier effect (SPE) in a Pt/yttrium iron garnet junction system has been investigated by means of a lock-in thermoreflectance method. We applied an alternating charge current to the Pt layer to drive SPE through the spin Hall effect, and measured the AC response of the resultant SPE-induced temperature modulation at frequencies ranging from 10 Hz to 1 MHz. We found that the SPE-induced temperature modulation decreases with increasing the frequency when the frequency is >1 kHz. This is a characteristic feature of SPE revealed by the high frequency measurements based on the lock-in thermoreflectance, while previous low frequency measurements showed that the SPE signal is independent of the frequency. We attribute the decrease of the temperature modulation to the length scale of the SPE-induced heat current; by comparing the experimental results with one-dimensional heat conduction calculations, the length scale of SPE is estimated to be 0.94 {\mu}m.