13:30 〜 13:45
▲ [16p-Z19-3] Enhancement of the anomalous Nernst effect in polycrystalline Co2MnGa/AlN multilayers
キーワード：anomalous Nernst effect, polycrystalline Co2MnGa, multilayer
Apart from the conventional thermoelectric generators devices utilizing the Seebeck effect (SE), its ferromagnetic counterpart, the anomalous Nernst effect (ANE), has gained increasing interests [1]. However, the reported thermoelectric conversion efficiency of the ANE is too small to realize the potential applications. Although “single crystal Co2MnGa” is a famous Heusler alloy exhibiting the large ANE [2], it has not been examined yet whether “polycrystalline Co2MnGa” also allows to achieve the large ANE or not. Meanwhile, previous study [3] suggests that the multilayering is a promising way to enhance the ANE. Here, we report a large ANE in a polycrystalline Co2MnGa/AlN multilayer film.
The film stacking structure is Si/SiO2/AlN(20)/[Co2MnGa(t)/AlN(5)]25/t (t = 2.5, 5.0, 12.5, and 25.0, unit in nm), which was fabricated by DC magnetron sputtering at room temperature followed by post-annealing at 500 oC for 3 hours. The largest anomalous Nernst thermopower (SANE) of 4.9 ± 0.1 µV K-1 was achieved for the multilayer film with t = 12.5 nm while SANE was obtained to be 3.8 ± 0.4 µV K-1 for the Co2MnGa single layer film with t = 25.0 nm. There are three possible scenarios for explaining the enhancement of ANE in the multilayer samples: (i) the higher chemical ordering promoted by interface stress, (ii) the change of band structure of distorted Co2MnGa grains, and (iii) composition variation via interdiffusion through the interface.
[1] Y. Sakuraba et al., Appl. Phys. Expr., 6, 033003 (2013). [2] A. Sakai, et al., Nat Phys. 14, 1119 (2018). [3] K. Uchida et al., Phys. Rev. B 92, 094414 (2015)
The film stacking structure is Si/SiO2/AlN(20)/[Co2MnGa(t)/AlN(5)]25/t (t = 2.5, 5.0, 12.5, and 25.0, unit in nm), which was fabricated by DC magnetron sputtering at room temperature followed by post-annealing at 500 oC for 3 hours. The largest anomalous Nernst thermopower (SANE) of 4.9 ± 0.1 µV K-1 was achieved for the multilayer film with t = 12.5 nm while SANE was obtained to be 3.8 ± 0.4 µV K-1 for the Co2MnGa single layer film with t = 25.0 nm. There are three possible scenarios for explaining the enhancement of ANE in the multilayer samples: (i) the higher chemical ordering promoted by interface stress, (ii) the change of band structure of distorted Co2MnGa grains, and (iii) composition variation via interdiffusion through the interface.
[1] Y. Sakuraba et al., Appl. Phys. Expr., 6, 033003 (2013). [2] A. Sakai, et al., Nat Phys. 14, 1119 (2018). [3] K. Uchida et al., Phys. Rev. B 92, 094414 (2015)