Critical suppression of spin Seebeck effect by magnetic fields

TL;DR

This study reveals that high magnetic fields critically suppress the longitudinal spin Seebeck effect in Pt/YIG systems, especially at low temperatures, highlighting the dominant role of low-frequency magnons in the effect.

Contribution

It introduces a magnon-frequency-dependent mechanism to explain LSSE suppression, emphasizing the importance of low-frequency magnons and the influence of YIG thickness.

Findings

High magnetic fields suppress LSSE voltage significantly.

Suppression is more pronounced at low temperatures.

YIG thickness affects the magnetic field dependence of LSSE.

Abstract

The longitudinal spin Seebeck effect (LSSE) in Pt/Y$_3$Fe$_5$O$_{12}$ (YIG) junction systems has been investigated at various magnetic fields and temperatures. We found that the LSSE voltage in a Pt/YIG-slab system is suppressed by applying high magnetic fields and this suppression is critically enhanced at low temperatures. The field-induced suppression of the LSSE in the Pt/YIG-slab system is too large at around room temperature to be explained simply by considering the effect of the Zeeman gap in magnon excitation. This result requires us to introduce magnon-frequency-dependent mechanism into the scenario of LSSE; low-frequency magnons dominantly contribute to the LSSE. The magnetic field dependence of the LSSE voltage was observed to change by changing the thickness of YIG, suggesting that the thermo-spin conversion by the low-frequency magnons is suppressed in thin YIG films due to the long characteristic lengths of such magnons.