Optimization of different strategies for designing an energy harvester based on spin-torque diodes

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Steadily growing demand for cheap and green energy has triggered a rapid development of so called ‘energy harvesting’ devices for producing dc-power from the ambient microwave radiation from various sources like TV and mobile-phone networks, Wi-Fi routers etc. The energy density of this radiation ranges from 1 to 1000 nW/cm^2, so that corresponding technology could be successfully used by low-power applications (digital thermometer, smoke detectors, some sensors in medicine etc.). The main goal of this project is the optimization of various designs for energy harvesters based on spin-torque-diodes, i.e. devices where dc-voltage is generated when an ac-current flows through a magnetic tunnel junction (MTJ). Using computer simulations, we intend to study and optimize three main types of MTJ-based nanodevices: (i) ‘standard’ MTJ nanopillars of the resonant type employing quasi-homogeneous in-plane magnetization oscillations; (ii) MTJs in the out-of-plane precession regime for broadband rectification and (iii) multilayer stacks with the specially designed in-plane layer shape where oscillation of domains walls (DWs) may occur.As results of this project we expect the determination of optimal geometric and magnetic parameters for all three kinds of spin-torque-based energy harvesters listed above, and the realistic prediction of the maximal rectification efficiency possible in actual environmental condition.