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

对廉价和绿色能源的稳定增长的需求引发了所谓的“能量收集”设备的快速发展，这种设备可以从电视和移动电话网络、Wi-Fi路由器等各种来源的环境微波辐射中产生直流电。这种辐射的能量密度从1到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、医学中的一些传感器等)。该项目的主要目标是优化基于自旋扭矩二极管的能量收集器的各种设计，即当交流电流流经磁性隧道结(MTJ)时产生直流电压的装置。通过计算机模拟，我们打算研究和优化三种主要类型的基于MTJ的纳米器件：(I)采用准均匀面内磁化振荡的共振型MTJ纳米管；(Ii)用于宽带整流的面外进动区域的MTJ；以及(Iii)具有特殊设计的面内层状的多层堆栈，其中可能发生磁区壁振荡(DWS)。作为该项目的结果，我们期望确定上述所有三种基于自旋扭矩的能量收集器的最佳几何和磁性参数，并对实际环境条件下可能的最大整流效率进行现实预测。

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.