Isolated and Collective Magnetic Phenomena in Metallic Nanocrystals and Their Superlattices

这项研究旨在将钝化的胶体纳米金属晶体合成、表征和组装成有序超晶格，其根本目的是了解它们的静态和动态磁性行为作为纳米晶体尺寸和形状、超晶格维度、组织对称性和晶间相互作用的函数的演化。这项工作的目的是使用磁测量方法来更深入地了解纳米结构的磁性计量学。这项研究将提供磁反转的基本机制，重点是有限大小和相互作用效应的作用，以及在没有粒子间交换相互作用的情况下偶极铁磁性的起源。这项研究着重研究了用于合成大面积(毫米尺寸)超晶格的熵驱动自组装和模板辅助结晶过程，以及利用电子和光子探针进行的系统的结构和化学表征。新出现的基于MEMS的计量方法和纳米晶体样品上的电子全息术将通过协作工作来研究。基本目标是彻底了解、预测和控制人工定制固体中不同长度尺度和时间特征的协作磁场行为。此外，这项工作将为与磁反转相关的基本问题提供解决方案。这项研究具有广泛的技术意义，因为它将有助于最终的磁记录介质的发展，即单粒子每比特记录以及MEMS技术。

The research is directed at the synthesis, characterization and assembly of passivated,colloidal nanocrystals of metals into ordered superlattices with the fundamental goal ofunderstanding the evolution of their static and dynamic magnetic behavior as a functionof nanocrystal size and shape, superlattice dimensionality, organizational symmetry andinterparticle interactions. The objective of the work is to use magnetometry methods to get a deeper understanding of the magnetic metrology of nanoscale structures. The study will provide fundamental mechanisms of magnetic reversal with emphasis on the role of finite size and interaction effects as well as the origin of dipolar ferromagnetism, in the absence of interparticle exchange interactions. The study emphasizes on the entropy-driven self-assembly and template-assisted crystallization processes for the synthesis of large-area (mm size) superlattices along with systematic structural and chemical characterization using electron and photon probes. Newly emerging MEMS based metrology methods and electron holography on the nanocrystal samples will be studied through collaborative work.The fundamental goal is a thorough understanding, prediction and control of cooperativemagnetic behavior over different length scales and time signatures in artificiallytailored solids. In addition, the work will provide solutions to fundamental questions associated with magnetic reversal. The research has broad technological implications for it will contribute to the development of the ultimate magnetic recording media, i.e. single-particle per bit recording as well as in MEMS technology.