Temperature dependence of the spin Seebeck effect in [Fe3O4/Pt]n multilayers

We report temperature dependent measurements of the spin Seebeck effect (SSE) in multilayers formed by repeated growth of a FeO/Pt bilayer junction. The magnitude of the observed enhancement of the SSE, relative to the SSE in the single bilayer, shows a monotonic increase with decreasing the temperature. This result can be understood by an increase of the characteristic length for spin current transport in the system, in qualitative agreement with the recently observed increase in the magnon diffusion length in FeO at lower temperatures. Our result suggests that the thermoelectric performance of the SSE in multilayer structures can be further improved by careful choice of materials with suitable spin transport properties.
This work was supported by the Spanish Ministry of Science (through projects MAT2014-51982-C2-R, including FEDER funding), the Aragón Regional Government (project E26), Thermo-spintronic Marie-Curie CIG (Grant Agreement No. 304043), JST-PRESTO “Phase Interfaces for Highly Efficient Energy Utilization” from JST, Japan, Grant-in-Aid for Scientific Research on Innovative Areas “Nano Spin Conversion Science” (26103005), Grant-in-Aid for Scientific Research (A) (15H02012) from MEXT, Japan, NEC Corporation, and The Noguchi Institute. T.K. is supported by JSPS through a research fellowship for young scientists (15J08026).