Novel Spintronic Microwave Devices

本提案旨在开发一组新型自旋电子微波器件。这些器件是基于自旋电子器件（如磁隧道结（MTJs））中的自由铁磁电极的磁化在微波存在下会进动，导致电阻变化的原理。检测微波功率的灵敏度和动态范围可与目前的射频二极管相媲美。MTJ传感器与射频二极管的区别在于，它们能够测量微波频率和相位，而无需使用传统的混频器进行外差检测。这大大简化了微波电路，并为小型化提供了机会。提出了自旋电子微波器件在网络分析、频谱分析和微波近场成像等领域的应用。本研究的目的是演示和理解这些提出的自旋电子微波器件。重要的器件问题，如灵敏度、动态范围和空间分辨率将被解决，并与磁阻比、偏置电压、铁磁共振和阻尼相关。一项旨在提高研究生就业机会的教育倡议也纳入了这项研究。智力上的优点包括在自旋电子器件中引入自旋动力学，以实现更多的功能，特别是在微波频率下。该器件原理基于与自旋转矩传递、自旋泵和自旋二极管效应所引入的现象根本不同的现象，但其简单性可能会立即影响并显著推进当前的微波技术。一些新的设计是基于以下事实：(a) MTJ器件本质上是非线性的，导致整流效应；(2)MTJ器件响应微波磁场，导致相位检测和信号增强的干扰效应；(3)微波电场和磁场都可以用来制造无源器件。广泛的影响包括对当前微波技术的可预见和极有可能立即产生的影响，特别是对网络分析仪、频谱分析仪和其他片上系统（SoC）产品的影响。这是可能的，因为自旋电子微波器件很小，不需要额外的电路，如混频器和移相器。这些特点也使固态微波近场成像成为可能。除了传统的教育和辅导外，我们将启动一个教育和推广项目，以扩大学生的就业机会，并开设一个急需的磁信息存储和微波磁学课程。这两门学科对于保持美国在当前全球经济中的竞争优势至关重要。

This proposal aims to develop an array of novel spintronic microwave devices. These devices are based on the principle that the magnetization of the free ferromagnetic electrode in spintronic devices such as magnetic tunnel junctions (MTJs) will precess in the presence of microwave, leading to a resistance change. The sensitivity and dynamic range for detecting microwave power is comparable to current RF diodes. What distinguishes MTJ sensors from RF diodes is that their capabilities to measure the microwave frequency and phase without using conventional mixers for heterodyne detection. This greatly simplifies microwave circuitry and offer opportunities for miniaturization. It is proposed to use spintronic microwave devices in applications like network analyzers, frequency spectrum analyzers, and microwave near field imaging. The objective of this proposed research is to demonstrate and understand these proposed spintronic microwave devices. The important device issues such as sensitivity, dynamic range, and spatial resolution will be addressed and related with magnetoresistance ratio, bias voltage, ferromagnetic resonance, and damping. An education initiative, targeting at enhancing career opportunity for our graduate students, is also integrated into this research. The intellectual merit includes introducing the spin dynamics in spintronic devices to achieve more functionalities, particularly at microwave frequencies. The device principles are based on the phenomena that are fundamentally different from those introduced from spin torque transfer, spin pumping, and spin diode effect, yet with simplicity that may immediately impact and significantly advance the current microwave techniques. Several novel designs are based on the facts that (a) a MTJ device is an intrinsically nonlinear which lead to a rectifying effect, (2) a MTJ device responds to microwave magnetic field which leads to interference effect for phase detection and signal enhancement, and (3) both microwave electric and magnetic fields can be used to create passive devices. The broad impacts include foreseeable and highly likelihood for immediate impacts on the current microwave technology, particularly in products of network analyzer, frequency spectrum analyzer, and other system on a chip (SoC). This is possible because spintronic microwave devices are small and does not need additional circuitry such as mixers and phase shifter. These features also make solid-state microwave near field imaging possible. Besides the traditional education and mentoring, we will initiate an education and outreach project in order to broaden career opportunities for our students and to develop a much needed course of magnetic information storage and microwave magnetics. Both subjects are critical to maintain the competitive edge of the Unite States of America in current global economy.