[10a-Z08-1~10] 10.2 スピン基盤技術・萌芽的デバイス技術

▼ [10a-Z08-2] All-optical detection of magnetization precession frequency shift due to spin-orbit torque

〇(M1)Kazuaki Ishibashi^1,2、Satoshi Iihama^3,4、Yutaro Takeuchi⁵、Kaito Furuya⁵、Shun Kanai^5,4,6,7、Shunsuke Fukami^5,4,6,2、Shigemi Mizukami^2,4,6 (1.Tohoku Univ.、2.Tohoku Univ. AIMR、3.Tohoku Univ. FRIS、4.Tohoku Univ. CSRN、5.Tohoku Univ. RIEC、6.Tohoku Univ. CSIS、7.Tohoku Univ. FRiD)

キーワード：spin-orbit torque, All-optical TRMOKE

Spin-orbit torque (SOT) has attracted considerable interest as a technique to manipulate magnetization for thin film. SOT has been mainly investigated using spin-torque ferromagnetic resonance and second harmonic Hall effect measurements. Even though these electrical methods are standard ways, it is known that there are parasitic voltages induced by spin-charge conversion and thermoelectric effect [1, 2]. Direct observation using all-optical measurement is free from such effects; thus it is a promising way. Previous studies have focused on the change in the relaxation time of the magnetization precession by SOT [3, 4]. Here we report the observation of the modulation of the precession frequency due to the SOT. The film stacking structure was Si/SiO₂/W(5)/CoFeB(2.4)/MgO(1.3)/Ta(1) (thickness in nm), which was fabricated by a DC/RF magnetron sputtering [5]. The film was patterned into a rectangular stripe. The magnetization precession modulated by SOT was investigated by an all-optical time-resolved magneto-optical Kerr effect microscope, in which an external field was applied at an out-of-plane angle θ and a direct current I was applied parallel to y-axis [Fig. 1(a)]. Figure 1(b) shows typical normalized signals measured with 0, ±5 mA. The modulation of the precession frequency was clearly observed. The result was well explained by the change in angle of precessional axis of magnetization induced by SOT and the SOT generation efficiency was evaluated as -0.35 [6]. This work was partially supported by KAKENHI (19K15430) and CSRN.