[26p-E201-1~12] 10.2 Fundamental and exploratory device technologies for spin

[26p-E201-1] [The 51st Young Scientist Presentation Award Speech] Origin of the background signal in spin torque ferromagnetic resonance

〇Motomi Aoki¹, Yuichiro Ando¹, Ei Shigematsu¹, Ryo Ohshima¹, Teruya Shinjo¹, Masashi Shiraishi¹ (1.Kyoto Univ.)

Keywords:spin orbit torque, spin rectification effect, unidirectional spin Hall magnetoresistance

Spin-torque ferromagnetic resonance (ST-FMR) has been widely used for estimation of the spin Hall angle (SHA) of a nonmagnetic material (NM). DC voltage, V_DC, in a NM/ferromagnetic metal (FM) bilayer structure is measured under microwave irradiation. When we plot V_DC as a function of external magnetic field, B_ext, V_DC-B_ext curve is sum of symmetric and anti-symmetric Lorentzian functions around the ferromagnetic resonance (FMR) field. By analyzing this resonance curve, SHA can be quantitatively estimated.
Whereas most researches using ST-FMR have focused on the V_DC-B_ext curve only around the FMR condition, background (BG) signals in the ST-FMR have been neglected because it does not affect curve fitting of the resonance spectrum. We found that the BG signal is produced by the spin-dependent unidirectional spin hall magnetoresistance, origin of which is the spin Hall effect of the NM. Therefore, analysis of the BG signal also gives the value of the SHA, which enables effective crosscheck for estimation of the SHA using the ST-FMR method. We also demonstrated detection of current-induced magnetization switching in W/Co bilayer system by using the BG signal.