[9a-E208-1~5] 10.1 Emerging materials in spintronics and magnetics (including fabrication and characterization methodologies)

10:00 AM - 10:15 AM JST(1:00 AM - 1:15 AM UTC)English Presentation

[9a-E208-5] Room-temperature sign reversal of anomalous Nernst thermopower in high-anisotropy quasi-2D topological nodal-line MnAlGe thin films

〇(PC)Nanhe Kumar Gupta¹, K Masuda¹, M Kakoki³, B Bairagya^1,2, S Tazawa^1,2, W Zhou¹, H Suto¹, A Kimura³, Y Sakuraba^1,2, R. Toyama¹ (1.NIMS, 2.U Tsukuba, 3.U Hiroshima)

Keywords:

Anamalous Nernst effect,,Topological Nodal line quaisi two dimenssional magnetic materials,High magnetic anisotropy thin film

The rapid growth of AI-driven microsystems, edge-AI devices, and high-density electronics has intensified the demand for efficient heat management and sensitive heat-flux detection. Heat-flux sensors based on the anomalous Nernst effect (ANE) offer an effective route for transverse thermoelectric conversion, making ANE polarity control essential for optimizing waste-heat harvesting and device performance [1]. However, achieving room-temperature polarity control in high-magnetic-anisotropy materials remains challenging [2]. Here, we demonstrate room-temperature sign reversal of ANE thermopower in MnAlGe, a high-anisotropy topological nodal-line ferromagnet [3], through systematic Al/Ge composition tuning (Fig. 1). The polarity reversal is attributed to Fermi-level tuning relative to the nodal-line electronic structure, supported by spin-resolved density of states calculations and hard X-ray photoemission spectroscopy. Importantly, the sign reversal is achieved while retaining a large magnetic anisotropy energy. We further demonstrate a device based on a meander structure, where combining the positive and negative polarity of MnAlGe enhances the device output. These results show that Fermi-level tuning while preserving high K_u enables controllable ANE polarity reversal within a single material, providing a route toward room-temperature transverse thermoelectric devices This work was supported by JST ERATO (No. JPMJER2201) [1] Y. Sakuraba, et al. Appl. Phys. Exp. 6, 3003 (2013). [2] S. Noguchi, et al. Nature Physics. 20, 254 (2024). [3] N.K. Gupta, et al. Phys. Rev. B. 113, 184404 (2026).