Voltage-based switching of memory elements based-on spin dephasing, diffusion and switching in ferrimagnetic metals

我们的经济和社会严重依赖信息技术，这消耗了越来越多的能源来处理和存储世界上的信息。这使得节能、非易失性存储系统成为未来计算机的关键目标。磁铁将信息编码成比特，这些比特通常是由具有极小尺寸的“北”极和“南”极的铁磁材料形成的，目前存储着大量的信息。然而，这些存储系统依靠磁场来操纵磁极，从而提供了一种具有非易失性存储但尺寸和能源效率有限的技术。本项目旨在通过利用所有的电气手段操纵纳米级非易失性磁存储器来实现一种基于具有反铁磁体和铁磁体性质的材料的低电流，称为亚铁磁体。亚铁磁体在一定温度下具有消失的磁化强度，可以通过精心设计的外加电场来改变磁化强度。该项目将为制造高能效、非易失性、纳米级的磁存储器和开关器件提供基本的科学知识和这一原理的演示。该项目将包括研究生和本科生的培训和外联活动，包括与学生物理俱乐部的合作、在线自旋电子学系列研讨会和棕色袋子研讨会。这个项目的重点是亚铁磁性金属合金和双层，总的目标是展示基于电压的存储元件开关，使用基于反常霍尔效应的检测方案，以及自旋传输传感器，如非局部自旋阀。一个特别的焦点是设计一种新的实验，同时测量亚铁磁性金属中的自旋退相长度和自旋扩散长度。这些对单一材料的测量将为一系列自旋电子系统和设备提供关键信息。该项目还将探索通过使用离子凝胶的电解门控来操纵电压。该项目探索了亚铁磁体的温度驱动开关，作为最终实现电压门控开关的第一步，这也可能被证明在传感方面的应用是有用的。研究活动将涉及亚铁磁性金属的表征和开发，包括SQUID磁测量以及使用独特的微米和纳米机械测量工具测量热电和热导率。该项目有四个主要方面：(1)开发、优化和表征用于亚铁磁性自旋电子学的材料，(2)测量亚铁磁性金属中的自旋消相和扩散长度，(3)使用亚铁磁体实现电压驱动的确定性磁开关，以及4)在亚铁磁性非局部自旋阀中调节自旋方向。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Our economy and society rely heavily on information technology, which consumes an ever-growing amount of energy to process and store the world’s information. This makes energy-efficient, non-volatile memory systems a critical goal for future computers. Magnets, where information is encoded in bits typically formed from ferromagnetic materials with “north” and “south” poles with very much reduced size, currently store a huge amount of information. However, these memory systems rely on magnetic fields to manipulate the poles, giving a technology with non-volatile storage but limited size and energy efficiency. This project aims to achieve a low-current, based on materials with properties of antiferromagnets and ferromagnets, called a ferrimagnet by using all electrical means of manipulating nanoscale non-volatile magnetic memory. A ferrimagnet has vanishing magnetization at a certain temperature which can be shifted with carefully engineered applied electric field. This project will provide fundamental scientific knowledge and demonstration of this principle, for the fabrication of energy efficient, non-volatile, nanoscale magnetic memory and switching devices. The project will involve graduate and undergraduate students training and outreach activities involving collaboration with the student physics club, online spintronics seminar series and brown bag seminars. This project focuses on ferrimagnetic metal alloys and bilayers, with the overall goal of demonstrating voltage-based switching of memory elements using a detection scheme based on the anomalous Hall effect, and of spin transport sensors such as non-local spin valves. One specific focus is on a design of a new experiment to measure both the spin dephasing length and the spin diffusion length in ferrimagnetic metals. These measurements for a single material, will provide critical information for a range of spintronic systems and devices. The project will also explore voltage manipulation via electrolytic gating using an ionic gel. The project explores temperature-driven switching of the ferrimagnet as a first step toward eventual voltage-gated switching, which could also prove useful for applications in sensing. Research activities will involve characterization and development of ferrimagnetic metals, including SQUID magnetometry and thermoelectric and thermal conductivity measurements using unique micro- and nanomachined measurement tools. The project has four main thrusts: (1) Developing, optimizing, and characterizing materials for ferrimagnetic spintronics, (2) Measuring the spin dephasing and diffusion lengths in ferrimagnetic metals, (3) Using a ferrimagnet to Realize Voltage-Driven Deterministic Magnetic Switching, and 4) Tuning spin direction in a ferrimagnetic non local spin valve.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.