Collaborative Research: Size-effect driven nanoparticle ferromagnetism

非技术摘要：磁性尺寸效应与所研究的磁性材料的磁性对尺寸的依赖性有关。像黄金这样的贵金属传统上不被认为是磁性材料，因为它们的块状形式缺乏永久磁性。然而，最近的研究表明，纳米材料可能具有截然不同的物理性质，实际上，贵金属在低于某些临界特征尺寸时可能会变得具有磁性。目前的研究项目是一个综合的研究和教育计划，以了解贵金属的磁性的大小依赖性。这是第一次详细研究贵金属纳米颗粒的磁性的尺寸和形状依赖性。各种技术被用来确定贵金属纳米颗粒的组成、尺寸和尺寸分布以及磁性。来自不同背景的幼儿园到高中的学生和本科生通过基于研究的指导计划参与这项研究。技术摘要：本提案的研究目的是检验将某些正常抗磁性金属的尺寸减小到纳米级可以导致铁磁性的假设。关于金等贵金属纳米粒子的铁磁性的报道被认为是有争议的，因为这些发现与公认的物理学相矛盾。激光加工技术正被用于在氧化物薄膜中合成所需尺寸的贵金属如金、银和钯的纳米颗粒样品。纳米颗粒在非磁性氧化物薄膜中的沉积同时提供了氧化物薄膜（氧化镁、氧化铝等）对纳米颗粒的合成、抑制团聚和原位钝化。详细的原子一级结构表征和高分辨率物理性质测量沿着元素特定磁化研究正在用于彻底表征样品。磁性研究包括纳米颗粒的静态和动态测量以及铁磁和电子顺磁共振研究。了解这些材料的尺寸依赖行为将阐明贵金属和近贵金属纳米粒子的铁磁性的起源。该项目支持2名研究生，涉及几名本科生。该提案的教育目标是：指导不同群体的高成就学生从事STEM职业，并为K-12 STEM招聘工作做出贡献。来自不同背景的本科生将参与我们基于研究的指导计划：通过热情和材料工程研究的意识（项目蒸汽）的成功。将对所有教育和外联活动进行评估，以监测方案的有效性，并为基于科学、技术、工程和数学的教育文献做出贡献。

Non-technical abstract:Magnetic size effects are related to the dependence of the magnetic properties on the dimensions of the magnetic material being studied. Noble metals like gold have not traditionally been considered as magnetic materials because of the lack of permanent magnetism in their bulk forms. However, recent research has shown that nanomaterials may have strikingly different physical properties and indeed noble metals may become magnetic below some critical feature size. The current research project is an integrated research and education program to understand the size dependence of the magnetic properties of noble metals. This is the first detailed study on the size and shape dependence of the magnetic properties of noble metal nanoparticles. A variety of techniques are being used to determine the composition, size and size distribution and magnetic properties of the noble metal nanoparticles. Students in kindergarten through high school and undergraduate students from diverse backgrounds are involved in this research via a research-based mentoring program. Technical abstract:The research objective of this proposal is to test the hypothesis that reducing the dimensions of certain normally diamagnetic metals to the nanoscale can result in ferromagnetism. Reports of ferromagnetism in noble metal nanoparticles like gold are considered controversial because the findings contradict well-established physics. Laser-processing techniques are being used to synthesize nanoparticle samples of noble metals like gold, silver and palladium of desired sizes in oxide thin films. Deposition of the nanoparticles in nonmagnetic oxide thin films simultaneously provides synthesis, suppressed agglomeration, and in-situ passivation of the nanoparticles by the oxide thin films (magnesia, alumina, etc.). Detailed atomic-level structural characterization and high-resolution physical property measurements along with element specific magnetization studies is being used to thoroughly characterize the samples. The magnetic studies include static and dynamic measurements and ferromagnetic and electron paramagnetic resonance studies of the nanoparticles. Understanding the size-dependent behavior of these materials will elucidate the origin of the ferromagnetism in noble and near noble nanoparticles. The project supports 2 graduate students and involves several undergraduate students. The educational objectives of this proposal are to: mentor a diverse group of high achieving students to STEM careers and contribute to K-12 STEM recruitment efforts. Undergraduate students from diverse backgrounds will be involved in our research-based mentoring program: Success Through Enthusiasm and Awareness of Materials Engineering Research (Project STEAMER). All of the educational and outreach activities will be assessed to monitor the efficacy of the programming and to contribute to the literature on STEM-based education.