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arXiv · 1504.00895

The effect of the magnon dispersion on the longitudinal spin Seebeck effect in yttrium iron garnets (YIG)

Hyungyu Jin·Stephen R. Boona·Zihao Yang·Roberto C. Myers·Joseph P. Heremans
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Abstract

We study the temperature dependence of the longitudinal spin-Seebeck effect (LSSE) in a yttrium iron garnet Y3Fe5O12 (YIG) / Pt system for samples of different thicknesses. In this system, the thermal spin torque is magnon-driven. The LSSE signal peaks at a specific temperature that depends on the YIG sample thickness. We also observe freeze-out of the LSSE signal at high magnetic fields, which we attribute to the opening of an energy gap in the magnon dispersion. We observe partial freeze-out of the LSSE signal even at room temperature, where kBT is much larger than the gap. This suggests that a subset of the magnon population with an energy below kB x TC (TC about 40 K) contribute disproportionately to the LSSE; at temperatures below TC, we label these magnons subthermal magnons. The T-dependence of the LSSE at temperatures below the maximum is interpreted in terms of a new empirical model that ascribes most of the temperature dependence to that of the thermally driven magnon flux.

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Hyungyu Jin, Stephen R. Boona, Zihao Yang, Roberto C. Myers, Joseph P. Heremans. 2015-04-03. The effect of the magnon dispersion on the longitudinal spin Seebeck effect in yttrium iron garnets (YIG). https://doi.org/10.1103/physrevb.92.054436

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