Giant Anomalous Nernst Effect in Polycrystalline Thin Films of Co2MnGa
Nakatsuji Group
Co2MnGa is a Heusler compound that exhibits the largest anomalous Nernst effect at room temperature. This effect arises from its topological band structure, namely, the Weyl cone. Previously, the large anomalous Nernst effects in thin films of Co2MnGa were obtained via epitaxial growth using a single-crystal substrate or an interface with an easily crystallized material such as AlN. Here, by improving the deposition process, we have succeeded in obtaining the anomalous Nernst effect of −5.4 μV/K in Co2MnGa polycrystalline films directly deposited on an amorphous template of SiO2/Si substrates, which are cheaper and readily available. The key aspect of this method is that Co2MnGa grains with the L21 structure were realized by high-temperature deposition. This film deposition technique can facilitate the commercial advancement of thermoelectric devices using the anomalous Nernst effect and the development of spintronics devices by interfacing with widened material classes.

Fig. 2. Column chart of absolute values of room-temperature anomalous Nernst effect (|Syx|)) obtained in magnetic materials. Each group is categorized as follows: bulk single crystals (green), bulk poly-crystals (brown), film deposited on a single crystalline substrate (blue), single-layer films deposited on an amorphous template (red), and multilayer films deposited on an amorphous template (purple).
References
- [1] R. Uesugi, T. Higo, and S. Nakatsuji, Appl. Phys. Lett. 123, 252401 (2023).