Magnetization dynamics in magnetic thin films for spintronic applications

Abstract

Spintronics provides an attractive pathway to next-generation logic, memory, and sensing devices. By harnessing the intrinsic angular momentum (spin) of electrons for data transport, processing, and storage, spintronic devices offer the advantages of low energy consumption, high operating frequency, non-volatility, and high endurance. To fully realize the potential of spintronic devices, it is crucial to understand spin dynamics in spintronic materials and to engineer materials and structures with desired properties. My Ph.D. Research projects embrace a series of efforts along this line to improve the performance of spintronic devices. Firstly, I focus on the stack design of L10-FePd, a promising spintronic material for achieving energy-efficient devices. I investigated the impacts of underlayer materials on the temperature-dependent magnetic anisotropy and Gilbert damping of L10-FePd. The results show that L10-FePd grown on different noble-metal underlayers has noticeable differences in temperature-dependent magnetic properties, which could be explained by different L10 phase ordering and spin pumping. Next, my interest shifts to exchange-coupled multilayer systems, particularly synthetic antiferromagnets with perpendicular magnetic anisotropy (p-SAFs). These systems are crucial building blocks for spintronics, enabling high operating speed and low energy consumption. Analytical results reveal the dynamic features in p-SAFs, including the amplitude, phase, and direction of precession. By comparing time-resolved magneto-optical Kerr effect measurements with the theoretical model, the effective anisotropic field and Gilbert damping of each ferromagnetic (FM) layer and the coupling constants and mutual spin-pumping parameters between two FM layers are extracted. Then I extend my p-SAF study to explore the dynamics of p-SAFs under strong magnetoelastic coupling. The preliminary results presented open the door to acoustic control of magnetization in p-SAFs, highlighting significant potential for reducing device energy consumption. Lastly, as material engineering heavily relies on material characterization, an effective way to advance the throughput of ferromagnetic resonance measurements is illustrated. Results show that by implementing optimal Bayesian experiment design, a 60% to 80% reduction in measurement time is achieved while maintaining the same level of result uncertainty.