Optical Studies of Spin Dynamics, Interfacial Magnetism, and Barrier Heights in MgO Heterostructures and Devices

技术：本项目利用光学技术研究MgO异质结构，这是一种重要的自旋电子材料。它的目的是解决几个重要的问题，关于巨隧穿磁阻（TMR）在基于氧化镁的磁性隧道结：TMR偏置依赖的来源，材料缺陷在TMR上的作用，以及关于自旋扭矩在横向和垂直方向上的磁性微观结构的有效假设。该项目应用光二次谐波产生（SHG）来直接解决这些重要问题，这些问题是基于mgo的磁隧道结和磁随机存取存储器的核心。在分子束外延（MBE）生长过程中，将利用二次谐波发生器对界面进行实时监测。它将用于表征界面磁性，并与体磁性进行比较。二次谐波产生还可以直接测量MgO的势垒高度和自旋分辨率，甚至可以提供与隧穿过程相关的有效质量信息。实验研究还将通过GHz交流电流共振驱动自旋扭矩器件的磁微观结构，并使用同步光脉冲测量界面和体磁化动力学之间可能的相移。此外，将开发一种无孔径近场光学显微镜技术，与时间分辨二次谐波产生光谱相结合，探测横向微观结构。非技术：该项目涉及材料科学主题领域的基础研究问题，具有高技术相关性。磁性随机存取存储器（MRAM）具有将现代生活各个方面使用的现有主流存储器结合成通用存储器的潜力。然而，挑战与前所未有的机遇并存。解决其中的一些挑战将极大地促进这项伟大技术的进步，从而对社会产生重大影响。参与该项目的学生将获得材料合成和光谱学方面的独特培训，这将有助于他们在工业就业市场的职业发展。由于加州大学河滨分校周围的人口结构多样化，因此有充足的机会帮助提高技术劳动力的多样性。pi致力于一系列的外展活动，包括本科生和高中参与研究，开发本科和研究生课程，以反映当前的研究活动，以及每周纳米物理期刊俱乐部的管理。

Technical: This project uses optical techniques to study MgO heterostructures, an important material for spin-based electronics. It aims to addressing several important questions regarding giant tunneling magnetoresistance (TMR) in MgO-based magnetic tunnel junctions: the source of the bias dependence of TMR, the role of materials imperfections on the TMR, and valid assumptions regarding magnetic microstructure in both the lateral and vertical directions for spin torque. The project applies optical second harmonic generation (SHG) to directly address these important issues which are central to MgO-based magnetic tunnel junctions and magnetic random access memory. Second harmonic generation will be utilized in situ to perform real-time monitoring of interfaces during molecular beam epitaxy (MBE) growth. It will be used to characterize interfacial magnetism and compare with the bulk magnetism. Second harmonic generation also has the ability to directly measure the barrier heights of MgO with spin resolution, and could even give information about the effective mass related to the tunneling process. The experimental research will also investigate magnetic microstructure in spin-torque devices by driving the devices resonantly with GHz ac currents, and used synchronized optical pulses to measure possible phase shifts between interface and bulk magnetization dynamics. In addition, an apertureless near-field optical microscopy technique will be developed to work in conjunction with the time-resolved second harmonic generation spectroscopy to probe the lateral microstructure.Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance. Magnetic random access memory (MRAM) possesses the potential to combine the existing mainstream memories, used in every aspect of modern lives, into a universal memory. However, the challenges coexist with this unprecedented opportunity. Solving some of the challenges will significantly contribute to the advances of this great technology, therefore have a great impact to the society. Students working on this project will gain a unique training in materials synthesis and optical spectroscopy, which will help them develop careers in the industrial job market. Due to the diverse demographic surrounding University of California at Riverside, there is ample opportunity to help enhance diversity in the technological workforce. The PIs are committed to a number of outreach activities including undergraduate and high school participation in research, development of undergraduate and graduate coursework to reflect the current research activities, and the management of a weekly nanoscale physics journal club.