Abstract
Ferromagnetic resonance (FMR) is an effective technique for probing the magnetization dynamics of magnetic thin films. In particular, bilayer systems composed of a paramagnetic layer and a ferromagnetic layer are commonly used for FMR-driven spin pumping experiments. Spin pump-and-probe models have been adopted to obtain the spin Hall angle (θSHE) and spin diffusion length (λN) for various single layer and bilayer systems. Trilayer systems, however, have rarely been studied with the same model. In this work, we study the structural asymmetry effect on Pt/Co/Pt trilayers and find that the different thicknesses of Pt on two sides of Co may change the spin current sign. Furthermore, we propose a method that allows analysis of Pt/Co/Pt trilayers using the spin pump-and-probe model. The obtained values of θPt and λPt in the Pt/Co/Pt system are 0.116 nm and 1.15 nm, respectively, which are consistent with the values obtained from other Pt-based bilayer systems.
Highlights
In 2004, Kato et al.1 first observed the spin Hall effect (SHE) experimentally in semiconductors through optical methods
The schematic illustration of ferromagnetic resonance (FMR) and spin pump-andprobe measurements is shown in Fig. 1, with θH defined as the angle between the applied field (H) and the sample plane, and w and l defined as the respective width and length of the sample, respectively
Effective magnetization increases with increasing magnetic anisotropy; in most spin pumping models, the calculation of spin mixing conductance treats the anisotropy as the angle of magnetization with respect to the sample plane
Summary
In 2004, Kato et al. first observed the spin Hall effect (SHE) experimentally in semiconductors through optical methods. Spin current is generated via ferromagnetic resonance (FMR) and injected into the adjacent heavy metal layer, resulting in an electrical signal which provides a quick way to acquire information of critical parameters such as spin diffusion length, spin mixing conductance, and spin Hall angle. In both the SHE and ISHE, the efficiency of spin–charge conversion can be expressed as the spin. To understand the “self-induced spin pumping” on the single layer system, a systematic study on the thickness dependent ISHE voltage was recently carried out on Co/Si and attributed to the combination of spin-orbit coupling and long spin diffusion length of Si. In this study, we design a Pt/Co/Pt trilayer system with different Pt thicknesses on two sides of Co and compare the results with the Co/Pt bilayer system to investigate the asymmetry effect on the ISHE
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