Collaborative Research: Size-Effect Driven Nanoparticle Ferromagnetism

The research objective of this proposal is to test the hypothesis that reducing the dimensions of normally diamagnetic metals to the nanoscale results in ferromagnetism. Reports of ferromagnetism in noble metal nanoparticles like gold (Au) are considered controversial because the findings contradict well-established physics. A room temperature (or higher) measurement showing magnetic hysteresis for clean nanoparticle samples would be convincing proof of the phenomenon. For those convinced that magnetism in noble metals like Au is a real effect, there is still controversy in understanding the underlying mechanisms. Typically, the noble metal nanoparticles have been synthesized using a solvent-based approach where the Au surface is capped by some type of organic ligand. We argue that the predominant fabrication methods do not allow true understanding of the intrinsic contribution to the magnetic moment due to the use of organics like thiols and due to incomplete surface encapsulation, which may result in quenching of magnetic moments at room temperature. To test this explanation, laser-processing techniques will be used to synthesize nanoparticle samples of noble metals like Au and silver (Ag) and palladium (Pd) of desired sizes in oxide thin films. Deposition of the nanoparticles in nonmagnetic oxide thin films will provide simultaneous synthesis, de-agglomeration, and in-situ passivation of the nanoparticles by the oxide thin films. Detailed atomic-level structural characterization and high resolution physical property measurements along with element specific magnetization studies will be used to thoroughly characterize the samples. 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 recruiting efforts. Undergraduate studentsvfrom diverse backgrounds will be involved in our research-based mentoring program Success Through Enthusiasm and Awareness of Materials Engineering Research (Project STEAMER). The PIs will work with existing efforts on their campuses to identify and mentor students. 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. The PIs’ collaboration with existing programs is highly synergistic, allowing for maximum impact of the education and outreach programs by using the different skills of the PI and collaborators. .