Electron Energy Levels in Magnetic Nanoparticles

Ralph这是一个新项目，研究被限制在直径小于10纳米的金属颗粒中的电子，以便在低温下可以分辨出离散的“盒子里的电子”能级。我们已经开发了制造包含单个纳米级金属颗粒的单电子隧道晶体管的技术，并且我们已经使用这些设备对纳米颗粒内的电子光谱进行了详细的测量。这种新能力是对电子结构的有力探测，因为所有作用在电子上的力都可以通过它们对特征态谱的单独影响来研究。在本提案中，我们将应用这些技术来研究磁性粒子。我们将(a)操纵单量子能级来研究自旋极化电子隧道效应，(b)检查磁性粒子中的电子谱，以了解交换力和它们产生的相关状态，以及(c)使用能级谱的时间依赖性研究作为纳米粒子磁矩动力学的探针。这是一个研究被限制在非常小的金属颗粒中的电子的新项目。当一块金属非常小，它包含的原子少于1万个时，金属内部的移动电子不能具有任意的能量，而是被限制在一组可分解的离散状态中。由于这种水平的离散性，这些小长度尺度上的电子设备可以被认为是“人造原子”。我们最近开发了一种技术，通过将电线连接到单个金属纳米颗粒上来生产晶体管设备，然后首次使用这些设备来测量金属颗粒内部允许能级的光谱。在本提案中，我们将应用这些新技术来研究磁性粒子。我们将研究(a)在什么条件下电子可以在不翻转自旋的情况下打开和关闭磁粒子，(b)磁力如何改变电子能级的谱，以及(c)粒子的磁性在外加磁场的影响下改变方向的机制。* * *

W:\awards\awards97 9705059 Ralph This is a new project to study electrons confined within metal particles less than 10 nm in diameter such that the discrete "electrons-in-a-box" energy levels become resolvable at low temperatures. We have developed techniques for fabricating single-electron tunneling transistors containing an individual, nm-scale metal particle, and we have used these devices to make detailed measurements of the electronic spectrum within the nanoparticle. This new capability is a powerful probe of electronic structure, because all the forces which act on the electrons can be studied through their separate effects on the eigenstate spectrum. In this proposal, we will apply these techniques to study magnetic particles. We will (a) manipulate single quantum levels to study spin-polarized electron tunneling, (b) examine the electronic spectrum in magnetic particles to understand exchange forces and the correlated states which they produce, and (c) use time-dependent studies of level spectra as a probe of the dynamics of the nanoparticle's magnetic moment. %%% This is a new project to study electrons confined in very small metal particles. When a piece of metal is so small that it contains fewer than 10,000 atoms, the mobile electrons inside the metal cannot have any arbitrary energy, but are limited to a resolvably discrete set of states. Because of the level discreteness, electronic devices on these small length scales can be thought of as "artificial atoms". We have recently developed techniques for producing transistor devices by connecting wires to individual metal nanoparticles, and then using these devices to measure the spectrum of allowed energy levels inside the metal particle for the first time. In this proposal, we will apply these new techniques to study magnetic particles. We will examine (a) under what conditions electrons can h op on and off a magnetic particle without flipping their spin, (b) how magnetic forces alter the spectrum of electron energy levels, and (c) the mechanisms by which the magnetism of the particle may switch direction under the influence of an applied magnetic field. ***