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HR)Ω(468ICYS Annual Report 2023 2µ0H (T)543210)T(2KH0µ)T()6(4KH0µMn(z= 0)Ge(z= 0)Mn(z= 1/2)Ge(z= 1/2)(a)0.05 Ω−8−6−4−20(b)(c)2-fold6-fold4-fold350 K300 K200 K0.60.40.20.0−0.2−0.4−0.6100 K10 K300320340360380Temperature (K)Yutaro TAKEUCHI1. Outline of Research2. Research ActivitiesFig. 1. Cross-sectional STEM image of the Mn3Ge(11¯00) epitaxial film. Atomic configuration is highlighted by circular symbols.Fig. 2. (a) R-H curves at different temperature. (b), (c) Temperature dependence of the effective field of two-, four- and six-fold magnetic anisotropies (HK2, HK4, HK6). µ0 represents the permeability in a vacuum.References1) P. Wadley et al., Science 351, 587 (2016).2) T. Jungwirth et al., Nat. Nanotech. 11, 231 (2016).3) S. Nakatsuji et al., Nature 527, 212 (2015).4) T. Higo et al., Appl. Phys. Lett. 113, 202402 (2018).5) T. Ikeda et al., Appl. Phys. Lett. 113, 222405 (2018)6) J.-Y. Yoon et al., Appl. Phys. Express 13, 013001 (2020).7) H. Tsai et al., Nature 580, 608 (2020).8) Y. Takeuchi et al., Nat. Mater. 20, 1364 (2021).9) Y. Takeuchi et al., APL Mater. 12, 071110 (2024).The progress in spintronics research demonstrated notable potential in nonvolatile memories and unconventional computing technology. Ferromagnets are commonly used as components of such functional devices, brought about by spintronic effects. In addition, antiferromagnets have recently attracted growing interest because of their unique attributes, such as negligible stray fields, robustness to external magnetic fields, and high-speed spin dynamics.1,2) These characteristics created a new paradigm in spintronics called antiferromagnetic spintronics. In particular, antiferromagnetic orderings with macroscopically broken time-reversal symmetry cause intriguing topological phenomena. Mn3X (X = Sn, Ge, Ga, and Pt) antiferromagnets have non-collinear magnetic texture in the Kagome lattice, and exhibit the large anomalous Hall effect (AHE) arising from the Berry curvature in momentum spaces.3) Topologically nontrivial effects of non-collinear antiferromagnets have been observed not only in bulk single crystals but also in thin films in recent years.4-6) These studies led to the current-induced control of magnetic texture in hexagonal D019-Mn3Sn.7,8) These advances in spintronic devices that use non-collinear antiferromagnets have inspired research into various materials for exploiting their potentials. In this study, we investigated the temperature dependence of the AHE and magnetic anisotropies in epitaxial D019-Mn3Ge films.9) Stacks consisting of W(5 nm)/Mn3Ge(50 nm)/Ta(2 nm) from substrate side were deposited on MgO(110) single-crystal substrate by magnetron sputtering. The nominal deposition temperatures of W, Mn3Ge, Ta layers are 400, 650, 100 oC, respectively. Figure 1 illustrates a cross-sectional STEM image of the Mn3Ge layer, indicating our template system with MgO(110) substrate and W(211) buffer layer leads to highly oriented epitaxial growth of Mn3Ge(11¯00). To perform magneto-transport measurements, the stacks were processed into Hall bar devices by photo lithography and Ar ion milling. Figure 2(a) shows the Hall resistance RH versus out-of-plane magnetic field H at various temperatures. The zero-field anomalous Hall effect is observed at wide temperature range of 10-350 K. We then evaluate in-Kagome-plane magnetic anisotropies by measuring magnetic field angle dependence of RH. Displayed in 2(b) and (c) is the effective field of two-, four-, and six-fold magnetic anisotropies. We found the dominant contribution of 2-fold component to the in-Kagome-plane magnetic anisotropy. Further, the effective field of 2-fold anisotropy obtained at 330 K is ~4 T, which is more than twice that of Mn3Sn5) at room temperature, thereby leading to higher thermal stability and robustness against the external field. Our results indicate the potential of Mn3Ge for future functional, high-speed, and high-density spintronics devices using antiferromagnets.the Research Digest 25Materials Research for High-Performance Antiferromagnetic Spintronics Devices