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▲ [16p-Z19-3] Enhancement of the anomalous Nernst effect in polycrystalline Co2MnGa/AlN multilayers
Keywords: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)