Time-Resolved Spin Dynamics in Ferromagnetic Microstructures

本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用于研究具有简单磁性微结构的单个纳米颗粒的激发光谱和自旋失相的起源。将发展对这些系统动力学的全面理解，包括与重要的自旋输运问题的联系。新的测量将提供有关磁场存在下的低洼激励、相互作用磁涡流的动力学以及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较小的纳米颗粒中自旋消相的起源，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将是金属和半导体器件中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在超快技术和纳米制造方面对研究生的培训，磁电子学的影响将得到加强。尺寸远小于1微米（人类头发的直径约为25微米）的小磁性颗粒已经被集成到计算机磁盘驱动器等技术中。新的电子器件已被提出，将小磁性元件与半导体元件（如晶体管）结合在一起。这个程序解决了控制小磁性粒子（有时被称为纳米粒子）行为的基本物理学，时间尺度小于一纳秒（十亿分之一秒）。相比之下，最先进的计算机磁盘上的一个“位”信息可以在大约一纳秒内写入。形状、内部结构和其他粒子存在的影响将使用一种非常快速的光学显微镜进行探索。这些实验将包括由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。新的超快磁性器件的发展将通过与其他大学项目以及当地工业的互动进行研究。

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.