The modulation of magnetization dynamics has attracted much attention for not only fundamental research but also application such as data processing and oscillators. It has been discovered that magnetization dynamics can be induced by spin transfer toque (STT) and spin-orbit-torque (SOT). The STT is exerted on the magnetization due to the spin angular momentum transfer, and the SOT occurs at the bilayer comprising a ferromagnetic metal (FM)/nonmagnetic heavy metal (HM).1 In this study, using the rectifying planar Hall effect (PHE), we investigate the SOT-induced magnetization dynamics in the multilayer consisting of HM/FM/Antiferromagnetic layer (AFM)/FM. Samples were pattered as the Hall bar device on a SiO₂/Si substrate were fabricated via microfabrication technique based on the lift-off method using magnetron sputtering process and electron beam lithography, as shown in Fig. 1. We fabricated the following system comprising 25-nm-thick N₈₁Fe₁₉/3-nm-thick NiO/5-nm-thick Ni₈₁Fe₁₉/Pt electrode on the substrate. An external magnetic field was applied at an angle θ from the one axis of the cross-type electrode, which was fixed parallel along to rf + dc electric current, as shown in Fig. 1. To measure the device, a ground-signal-ground (GSG)-type microwave probe was connected to the electrode. Using a home-made automatic rotating magnetic field application system, we evaluate the simultaneous magnetoresistance and PHE properties as a function of θ. Figures 2(a) shows a typical rectifying PHE voltage spectrum obtained at θ = 15°. The magnetic field angle dependences of these rectifying voltages are found to be in good agreement with the analytical prediction curves of cos2θcosθ. 2 Figure 2(b) displays the resonance frequency as a function of dc current, I_dc. The resonance frequency is linearly decreased with increasing I_dc. Full width at Half Maximum (FWHM) is also linearly modulated by the application of I_dc. These results indicate that the magnetization dynamics can be modulated by the spin current in the multilayer structure.
References
1 X. Qiu, K. Narayanapillai, Y. Wu, P. Deorani, D. –H. Yang, W. –S. Noh, J. H. Park, K. –J. Lee, H. –W. Lee, and H. Yang, Nat. Nanotechnol. 10, 333 (2015). 2 A. Yamaguchi, A. Hirohata, B. Stadler, Nanomagnetic Materials: Fabrication, Characterization and application, Elsevier, 2021.

Figure 1 Schematic circuit of measurement and optical micrograph of system.

Figure 2(a) Typical rectifying PHE spectrum obtained at θ=15°. (b) dc current dependence of resonance frequency.