[17p-501-1~7] 10.1 新物質・新機能創成（作製・評価技術）

▲ [17p-501-1] Tuning the magnetic properties and surface morphology of D0₂₂ Mn_3-δGa film by N doping

〇(PC)Lee Hwachol¹、Sukegawa Hiroaki¹、Liu Jun¹、Mitani Seiji^1,2、Hono Kazuhiro^1,2 (1.NIMS、2.Univ. Tsukuba)

キーワード：MnGaN, MnGa, perpendicular magnetic anisotropy

Recently, tetragonal Mn-based alloys such as L1₀ and D0₂₂ Mn-Ga alloys [1] have been of great concern in search of new magnetic alloy systems with low Gilbert damping, low saturation magnetization M_s, and high perpendicular magnetic anisotropy K_u for potential applications such as a next generation spin transfer torque-magnetic random access memory. In this work, we present tuning the magnetic properties and surface morphology of D0₂₂ Mn_3-δGa using a small amount of N doping [2]. 50 nm thick N-doped MnGa films were prepared by RF reactive sputtering technique on an MgO(001) single crystalline substrate at 480°C substrate temperature with the varied 0-0.66% N₂ flow rate percentage (η) relative to Ar 30 sccm for two Mn₃Ga and Mn_2.5Ga compositions. N-doped Mn-Ga films all exhibited the gradual reduction in M_s up to 33-50% with the increasing N₂ flow rate as in Fig. 1 (a). In particular, N-doped Mn_2.5Ga case revealed the single D0₂₂ structural phase formation with the high K_u ≈ 1 MJ/m³ between η = 0-0.66% range despite the gradual reduction in magnetization, while N-doped Mn₃Ga showed coherent growth of two D0₂₂ + E2₁ composite phases which results in the further reduction in M_s and K_u < 1 MJ/m³, as in Fig. 1 (b). In addition, N doping in both Mn₃Ga and Mn_2.5Ga caused the smoothening of the surface morphology with the increasing film thickness up to 50 nm even with the use of the minimum η of 0.25%, as shown in the inset of Fig. 1, which represents the modification of the film growth mode from Volmer-Weber type of D0₂₂ Mn-Ga case at this high 480°C growth temperature. Therefore, these results suggest that a small amount of N doping is an effective way of tuning the magnetic properties of D0₂₂ Mn_3-δGa films in addition to obtaining a flat surface at high growth temperature. This work was partly supported by Samsung Electronics.

References:
[1] S. Mizukami, A. Sakuma, A. Sugihara, K. Z. Suzuki, and R. Ranjbar, Scripta Mater. 118, 70 (2016).
[2] H. Lee, H. Sukegawa, J. Liu, S. Mitani, and K. Hono, Appl. Phys. Lett. 109, 152402 (2016).