Minimal influence of interfacial magnetic anisotropy on the anomalous Nernst effect

Abstract

The anomalous Nernst effect (ANE) plays a crucial role in thermoelectric energy conversion. Recent studies have suggested that ANE can be enhanced by increasing magnetic anisotropy, based on investigations of ferromagnetic alloys such as FePt, FePd, and MnGa, which possess varying degrees of magnetic anisotropy. Moreover, it has been reported that interfacial effects can also significantly influence the ANE. However, these materials differ not only in anisotropy but also in other intrinsic properties, leaving it unclear whether uniaxial magnetic anisotropy alone plays a decisive role in enhancing ANE. To isolate the effect of magnetic anisotropy, we studied MgO/Ta/CoFeB/W thin films, where voltage-controlled magnetic anisotropy enables modulation of magnetic anisotropy without altering other material characteristics. Despite a 30% reduction in magnetic anisotropy, we observed less than a 3% change in ANE, indicating a weak correlation. These findings suggest that magnetic anisotropy alone is not a critical factor governing the ANE, and that the ANE remains robust in voltage-tuned devices.