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Spin Transfer Driven Magnetization Dynamics in Magnetic Nanopillars

November 16, 2012 11:00AM to 12:00PM
Presenter 
Huanlong Liu, New York University
Location 
Building 223, Room S105
Type 
Seminar
Series 
Materials Science Seminar
Abstract:
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.