[13p-S302-1~15] 10.1 Emerging materials in spintronics and magnetics (including fabrication and characterization methodologies)

▲ [13p-S302-1] Two-dimensional Electronic State in a Ferromagnetic L1₀ MnGa Thin Film with Perpendicular Magnetization

〇MASAKI KOBAYASHI^1,2, N. H. D. Khang³, Takahito Takeda¹, Kohsei Araki¹, Ryo Okano¹, Masahiro Suzuki⁴, Kenta Kuroda⁵, Koichiro Yaji⁶, Katsuaki Sugawara^7,8,9,10, Seigo Souma^8,9, Kosuke Nakayama^7,10, Miho Kitamura¹¹, Koji Horiba¹¹, Atsushi Fujimori^4,12, Takafumi Sato^7,8,9,5, Shik Shin⁵, Masaaki Tanaka^1,2, Pham Nam Hai^2,3 (1.Grad. Sch. Eng., Univ. of Tokyo, 2.CSRN, Univ. of Tokyo, 3.Tokyo Tech., 4.Dep. Phys., Univ. of Tokyo, 5.ISSP, Univ. of Tokyo, 6.NIMS, 7.Dep. Phys., Tohoku Univ., 8.WPI-AIMR, Tohoku Univ., 9.CSRN, Tohoku Univ., 10.JST-PREST, 11.KEK-IMSS, 12.Dep. Appl. Phys., Waseda Univ.)

Keywords:Perpendicular magnetization, Electronic state, Angle-resolved photoemission spectroscopy

Ferromagnetic thin films with perpendicular magnetization are key materials for high-density magnetic recording and other spintronics applications. Mn_1-xGa_x thin films with the L1₀ (or CuAu type) crystal structure (referred to as MnGa), which show strong perpendicular magnetic anisotropy (PMA), were successfully grown by molecular beam epitaxy (MBE) in the early 1990s. Recently, spintronic device structures using MnGa layers have been studied, such as magnetic tunnel junctions and spin-orbit torque devices. To understand the properties of MaGa and the heterostructures using MnGa, it is important to characterize the electronic properties of MnGa. In this study, we have performed angle-resolved photoemission spectroscopy (ARPES) with vacuum ultra-violet light on a L1₀ MnGa thin film with PMA to elucidate the electronic states.
The in-plane Fermi surface mapping demonstrates a diamond-like Fermi surface (FS) in the k_x-k_y (the [100] and [010] directions) plane. The large area of FS is consistent with the metallic nature of MnGa. This FS was likely independent of photon energy, indicating that the FS originates from two-dimensional (2D) bands. In contrast, the bulk band dispersion below the Fermi level changes with k_z. Since MnGa has the three-dimensional L1₀ crystal structure, the observed 2D electronic state is expected to come from surface states. To the authors’ knowledge, this is the first observation of the band dispersion in a MnGa film with the clean surface using ARPES.