Collaborative Research: Size-effect driven nanoparticle ferromagnetism

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

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 are 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.