Collaborative Research: Spin Torque Oscillators Based on Electric and Thermal Spin Currents in Self Assembled Ferromagnetic Nanowire Arrays

建议活动的智能优点：该项目旨在利用自组装铁磁纳米线的有序阵列来研究由电和热自旋电流驱动的自旋转移扭矩，并研究这些紧密堆积的自旋扭矩振荡器阵列中的非线性磁化动力学。这项合作研究的目标是：(I)研究铁磁纳米线产生的电和热自旋矩对电位和温度梯度的响应；(Ii)研究六方排列的强耦合自旋转移扭矩振荡器阵列中的非线性集体磁化动力学；以及(Iii)开发基于锁相自旋扭矩振荡器阵列的高功率微波压控振荡器。这些纳米线将作为自旋电流注入器，注入到所有注入器共有的铁磁性薄膜中。自旋电流将通过施加在纳米线上的电压或温度梯度来产生。在共同的铁磁层中传播的自旋波将促进各个自旋扭矩振荡器之间的耦合。磁动力学的超快电检测、宽带铁磁共振和磁力显微镜将被用来表征自旋扭矩振荡器阵列中的非线性磁化动力学。这项研究将加深对电流和自旋电流驱动的大幅值磁化动力学的理解，这对于开发下一代超快和非易失性磁电子器件，如硬盘读取头和无线通信系统具有重要意义。这项研究计划还将对同一系统中更常见的自旋极化电流与热驱动自旋电流的相对强度进行基准测试。拟议活动的广泛影响：本研究开发的微波压控振荡器将对信息存储和电信行业产生重大技术影响。博士生以及本科生和高中生将在调查人员的指导下参加这个项目。该计划提供的纳米制造和独特测量技术方面的实践培训将为美国磁电子行业培养专家，目前美国磁电子行业正经历着从微米到纳米的快速过渡。私人机构将继续吸引少数族裔服务机构(如加州州立大学)的代表不足的学生以及本地K-12学生参与研究项目。在教育课程中，所有研究人员都开发了纳米科学和纳米技术课程，并为研究生和本科生提供了一系列演示。该项目由电子、通信和网络系统部门(ECCS)的电子、光子学和磁性设备计划(EPMD)和材料研究部门(DMR)的电子和光子材料计划(EPM)共同资助。

Intellectual merit of the proposed activity: The project aims to study spin transfer torques driven by electric and thermal spin currents by utilizing ordered arrays of self-assembled ferromagnetic nanowires, and to investigate the nonlinear magnetization dynamics in these closely packed spin torque oscillator arrays. The objectives of this collaborative research are: (i)to study electric and thermal spin torques generated by a ferromagnetic nanowire in response to electric potential and temperature gradients; (ii) to study nonlinear collective magnetization dynamics in the hexagonally packed two dimensional arrays of strongly coupled spin transfer torque oscillators; and(iii)to develop a high-power microwave voltage controlled oscillator based on an array of phase locked spin torque oscillators.The proposed array of spin torque oscillators consist of hexagonally ordered cobalt nanowires electrodeposited in anodized alumina template. These nanowires will serve as spin current injectors into a thin ferromagnetic film common to all injectors. Spin currents will be generated by either voltages or thermal gradients applied across the nanowires. Coupling among the individual spin torque oscillators will be facilitated by spin waves propagating in the common ferromagnetic layer. Ultrafast electrical detection of magneto-dynamics, broadband ferromagnetic resonance and magnetic force microscopy will be used to characterize the nonlinear magnetization dynamics in the array of spin torque oscillators. The proposed research will advance the understanding of the large-amplitude magnetization dynamics driven by electric and spin currents, which is important for the development of the next generation ultrafast and non-volatile magneto-electronic devices such as hard drive read heads and wireless communication systems. This research program will also benchmark the relative strength of thermally driven spin currents against the more common spin-polarized electric currents in the same system.Broader impact of the proposed activity: The microwave voltage controlled oscillator developed in this research will have a significant technological impact on information storage and telecommunication industries. PhD students, as well as undergraduates and high school students will take part in this program under the guidance of the investigators. The practical training in nanofabrication and unique measurement techniques offered by this program will prepare specialists for the USA magneto-electronics industry that are currently undergoing a rapid transition from micro- to nano-scale. The PIs will continue to attract underrepresented students from minority-serving institutions, such as California State Universities, as well as local K-12 students to participate in the research projects. In the education curriculum, all investigators have developed courses on nanoscience and nanotechnology with a series of demonstrations for graduate and undergraduate students.This project is jointly funded by the Electronics, Photonics, and Magnetic Devices Program (EPMD) in the Division of Electrical, Communications and Cyber Systems (ECCS) and by the Electronic and Photonic Materials Program (EPM) in the Division of Materials Research (DMR).