films*

Recently, the spin Seebeck effect (SSE) in antiferromagnetic (AFM) Cr₂O₃ and MnF₂ has been reported and the signals were found to rise significantly above the spin-flop (SF) field. However, it is still unclear whether the SSE requires an induced magnetic moment or just the presence of AFM magnons. Here we report a study of the SSE of FeF₂/Pt heterostructures in which FeF₂ is an insulating AFM epitaxial film. The high SF field (42 T) of FeF₂ makes it a perfect candidate for studying the SSE below the SF field. The AFM properties of FeF₂ film are characterized by exchange bias. The SSE signal of FeF₂/Pt under different magnetic fields shows very similar temperature-dependent behaviors. First, there is a peak at around 11.6 K due to AFM-magnons’ contribution. Second, we observe a “bump” at the AFM ordering temperature (70 K), beyond which the SSE signal decays and persists up to 250 K under high magnetic fields, indicating that short-range spin fluctuations also contribute to the SSE signal.