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

对廉价和绿色能源不断增长的需求促使所谓的“能量收集”设备迅速发展，这种设备从电视、移动电话网络、Wi-Fi路由器等各种来源的环境微波辐射中产生直流电。该辐射的能量密度范围为1至1000 nW/cm^2，因此相应的技术可以成功地用于低功耗应用（数字温度计，烟雾探测器，一些医学传感器等）。该项目的主要目标是优化基于自旋扭矩二极管的能量采集器的各种设计，即当交流电流过磁隧道结（MTJ）时产生直流电压的设备。利用计算机模拟，我们打算研究和优化三种主要类型的MTJ纳米器件：(i)谐振型的“标准”MTJ纳米柱，采用准均匀的平面内磁化振荡；（ii）用于宽带整流的面外进动区MTJs和（iii）具有特殊设计的面内层形状的多层堆栈，其中可能发生畴壁振荡（DWs）。作为本项目的结果，我们期望确定上述三种基于自旋力矩的能量采集器的最佳几何和磁性参数，并现实地预测实际环境条件下可能的最大整流效率。

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.