Time-Resolved Spin Dynamics in Ferromagnetic Microstructures

这项研究计划将研究亚微米铁磁粒子的自旋动力学。皮秒时间分辨克尔显微镜将被用来研究具有简单磁性微结构的单个纳米粒子的激发光谱和自旋脱相的起源。我们将全面了解这些系统的动力学，包括与自旋输运这一重要问题的联系。新的测量将提供有关磁场存在时的低激发、相互作用的磁涡的动力学以及磁畴壁对亚纳秒电流脉冲的响应的信息。第二个研究领域集中在更小的纳米粒子中自旋退相的起源，其中将探索通过产生非均匀自旋波模式来抑制相干性。该计划解决的第三个问题是金属和半导体器件中的自旋动力学和自旋输运之间的关系。通过与材料科学家的合作以及对研究生进行超快技术和纳米制造方面的培训，将加强对磁电子学的影响。尺寸远小于一微米(一根头发的直径约为25微米)的微小磁性颗粒已经集成到计算机磁盘驱动器等技术中。已经提出了将小型磁性元件与晶体管等半导体元件相结合的新型电子设备。这个项目解决了控制微小磁性粒子(有时被称为纳米粒子)行为的基本物理学，其时间尺度不到一纳秒(十亿分之一秒)。相比之下，最先进的计算机磁盘中的一位信息可以在大约一纳秒内写入。我们将使用一种非常快速的光学显微镜来探索形状、内部结构和其他颗粒的存在的影响。这些实验将涉及研究生开发新的光学和微波技术，以及与材料科学家的重要合作。将通过与其他大学项目和当地行业的互动来研究新的超快磁性设备的开发。

This research program will study the spin dynamics of sub-micron ferromagnetic particles. Picosecond time-resolved Kerr microscopy will be used to study the excitation spectra and origins of spin dephasing in individual nanoparticles with simple magnetic microstructures. A comprehensive understanding of the dynamics of these systems will be developed, including connections to the important problem of spin transport. New measurements will provide information about low-lying excitations in the presence of a magnetic field, the dynamics of interacting magnetic vortices, and the response of domain walls to sub-nanosecond current pulses. The second area of research focuses on the origins of spin dephasing in smaller nanoparticles, in which the suppression of coherence by the generation of non-uniform spin-wave modes will be explored. The third problem addressed by this program will be the relationship between spin dynamics and spin transport in both metallic and semiconductor devices. The impact on magneto-electronics will be enhanced through collaborations with materials scientists as well as the training of graduate students in ultrafast techniques and nanofabrication. Small magnetic particles, with dimensions much less than one micron (a human hair has a diameter of about 25 microns), are already integrated into technologies such as computer disk drives. New electronic devices have been proposed that combine small magnetic elements with semiconductor components such as transistors. This program addresses the fundamental physics that governs the behavior of small magnetic particles, sometimes called nanoparticles, on time scales of less than a nanosecond (one billionth of a second). For comparison, a "bit" of information in a state-of-the-art computer disk can be written in about one nanosecond. The effects of shape, internal structure, and the presence of other particles will be explored using a very fast form of optical microscopy. The experiments will involve the development of new optical and microwave techniques by graduate students as well as significant collaboration with materials scientists. The development of new ultrafast magnetic devices will be investigated through interactions with other university programs as well as local industry.