Novel Spintronic Microwave Devices

University Of Delaware, Newark DE

Investigators

Abstract

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.