The Longitudinal Spin Seebeck Coefficient of Fe

We report an experimental study of the longitudinal spin Seebeck effect (LSSE) of a Fe thin film with a Pt detection layer. By varying the Fe thickness, we find that the anomalous Nernst effect (ANE) of Fe changes sign and vanishes at about 4.8 nm. This provides a unique opportunity to study the LSSE where the influence of ANE is absent. The addition of a 3 nm Pt layer produces a considerable thermal voltage, which comes from the LSSE of Fe solely. The opposite signs of thermal voltages in Pt/Fe and W/Fe bilayer structures confirm that the signal is dominated by LSSE because Pt and W have opposite signs of spin Hall angle. In conjunction with the Pt-thickness-dependent measurement of effective spin-mixing conductance of Fe/Pt films, we estimate the spin Seebeck coefficient of Fe.