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 (SANE) decreased with x from 1.7 to 0.6 μV/K and the Seebeck coefficient increased with x from −2.3 to 1.2 μV/K. The transverse thermoelectric conductivity (αxy) evaluated from the experimental data showed a decrease with x and the change of αxy dominated the change of SANE. The anomalous Hall conductivity and αxy 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.