Microwave Amplification by Spin Transfer Emission .. (MASTER)
Microwave Amplification by Spin Transfer Emission Radiation
Start date: Sep 1, 2008,
End date: Feb 29, 2012
The intended aim of this project is to explore the application potential of novel Spin-Transfer Oscillators (STO) as tunable and ultra-narrow band microwave radiation sources for mobile and wireless telecommunication technology. The main technological interest of STO devices, which correspond to nano-structured magnetic multilayer pumped by a spin-polarized electrical current and emitting microwave radiation, is their compatibility with monolithic integration. Our proposal specifically addresses the bottleneck issue of power conversion efficiency between dc current pumping and microwave emission of radiation. We propose to take advantage of the phase-locking mechanisms between coupled oscillators to increase significantly the device performance. Our primary objective is to engineer large arrays of coherently coupled oscillators. To achieve this goal, we shall investigate in detail 4 different types of coupling mechanism between neighboring oscillators which may induce phase-locking of the ensemble: 1) coupling through the self-generated microwave current, 2) coupling through the dipolar magnetic field, 3) coupling through the spin-diffusion of the conduction electrons, 4) coupling mediated by spin-waves. Achieving phase-locking between neighboring oscillators also requires substantial progress in our understanding of the fundamental mechanisms that are involved during momentum-transfer from spin-polarized current to the magnetic moments. Our secondary objective is to address both experimentally and theoretically 3 knowledge gaps: identifying (spatio-temporal profile and relaxation times) the fundamental spin-wave eigen-modes excited by a dc current in nano-structured magnetic heterojunctions; understanding the fundamental mechanism underlying non-local effects associated with the diffusion of spin-polarized electrons and its action on the dynamics of the whole system; investigating the magnetization dynamics of a nano-structure in the non-linear regime.
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