Spin Transfer Driven Magnetization Dynamics in Magnetic Nanopillars
The interaction between the intrinsic spin of itinerant electrons and the magnetization of ferromagnetic materials is of great interest for both fundamental physics and applications. While a thick ferromagnetic layer can polarize the spin of the electrons passing through, a spinpolarized current can also transfer the angular momentum to the magnetization via spin-transfer torque (STT) and change the magnetization orientation correspondingly.
We experimentally study the magnetization reversal, relaxation and precession in magnetic nanostructures such as spin-valves and magnetic tunnel junctions (MTJs) subject to spin-polarized current, as well as applied magnetic field and thermal fluctuation. We explore the magnetization dynamics in a wide range of timescales, from sub-nanosecond to second and we are able to resolve these dynamics in real-time under 50 ps. We examine the magnetization configurations by resistance measurements through Giant Magnetoresistance (GMR) and Tunnel Magnetoresistance (TMR) effects. We use a macro-spin model with analytical solutions for direct comparison with experimental data on spin-valves with perpendicular anisotropies. We also carry out a Fokker- Planck calculation in order to address the influence of thermal fluctuation on magnetization dynamics.
This research was supported at NYU by NSF Grant No. DMR- 0706322, DMR- 1006575, USARO Grant No. W911NF0710643, the Partner University Fund (PUF) of the Embassy of France and Spin Transfer Technology.