[23a-A205-1~13] 10.2 スピン基盤技術・萌芽的デバイス技術

▼ [23a-A205-2] Double heterostructure introduction in Pt/Ni/Co system for skyrmion with small size and fast transport

〇(M2)Lin Zhang¹、Ryuta Satone¹、Xiaorui Ya¹、Yuichiro Kurokawa¹、Takehiro Tamaoka¹、Yuto Tomita¹、Hongye Gao¹、Satoshi Hata¹、Yasukazu Murakami¹、Terumitsu Tanaka¹、Hiromi Yuasa¹ (1.Kyushu Univ.)

キーワード：skyrmions

Magnetic skyrmion is thermodynamically stable quasi-particle and attracting attention as a novel data carrier owing to its advantage; nano-scale size, and fast transport by low current [1]. However, these advantages do not realize simultaneously, that is the trilemma. For details, the transport velocity is increased by increasing the electric current for spin orbit torque, but decreased by decreasing the skyrmion size. To solve the problem, there is several approaches; increase of spin Hall angle in heavy metal, high spin mixing conductance at the interface, and reduction of saturation magnetization of magnetic layer. In this report, we focus on the control of the spin mixing conductance by the double heterostructure which is realized by inserting the ultra-thin layer between Pt and Co. Until now, it has been reported that the insertion layers improved the spin mixing conductance in spin Seebeck effect and spin Hall magnetoresistance [2]. At the interface, on the other hand, the suitable Dzyaloshinskii-Moriya interaction is necessary to form skyrmion. Although it has reported that the Co/Pt interface has the DMI around 0.2 mJ/m² [3], there is concern that DMI is reduced by insertion layer. Therefore, we investigated the lower limit condition of DMI by using micromagnetic simulation MuMax3 [4, 5]. Then, in experimental, the required condition was found for the high spin mixing conductance and high DMI in the Pt/insertion layer/Co/Ni system. The reference film structure is Ta 2nm/Pt 5nm/[Co 0.7nm/Ni 0.5nm/Pt 0.7nm]₃₀/Ta 5nm, whose MH curve and Lorentz TEM images are shown in Fig. 1 and 2. The typical skyrmions were observed near the saturation magnetic field. Since the various insertion materials were reported to increase spin mixing conductance, also various materials less than 1.0 nm was inserted here. In the presentation, we will show the comparison of conditions for skyrmion generation between without and with insertion layer.