Anomalous Nernst effect in epitaxially grown Fe4-xNixN films

Anomalous Nernst effect of epitaxial Fe4-xNixN films on MgAl2O4(001) substrates was characterized. The Ni/Fe ratio (x) in Fe4-xNixN films was changed in the range of 0 <= x <= 2.8, and the Fe4-xNixN phase started to decompose into FeNi at about x = 2.2. The anomalous Nernst coefficient (S-ANE) decreased with x from 1.7 to 0.6 mu V/K and the Seebeck coefficient increased with x from -2.3 to 1.2 mu V/K. The transverse thermoelectric conductivity (alpha(xy)) evaluated from the experimental data showed a decrease with x and the change of alpha(xy) dominated the change of S-ANE. The anomalous Hall conductivity and alpha(xy) of Fe4N and Fe2.8Ni1.2N were obtained by first-principles calculations, showing a significant difference from the experimental results, which might be caused by the contribution from the extrinsic mechanisms.