CAREER: Short-Range Order as Design Parameter for Topological Magnetism

About This Grant

Non-technical abstract: This project aims to identify factors that affect magnetic properties of non-crystalline solid-state materials that they can be used for future microelectronics, including neuromorphic computing. The short-range order of disordered atoms of magnetic metals and non-magnetic semiconductors has a profound impact on, e.g., the onset of magnetism and resistivity that govern the functionality of the magnetic films. The arrangement and orientation of atoms is influenced by the synthesis and can be modified afterwards by strain and curvature. This research, exploring the potential of such a new means of manipulation, is integrated with education efforts, which aim to combine mentoring, evidence-based teaching, and outreach with research to stimulate interest in science and science-driven art creation. This includes: (1) an outreach program at the nexus of physics and art that uses visualization to engage high school juniors and seniors in fundamental physics; (2) a new advanced characterization graduate course to address real-world problems; and (3) research and mentorship opportunities for high school seniors, undergraduate, and graduate students. These efforts revolve around the hypothesis that visualizing science and physical mechanisms fosters curiosity of diverse students (from high school through graduate school) and facilitates knowledge and innovation. Technical abstract: Advancing our limited understanding of amorphous quantum materials–an emerging research field with properties defying traditional physics knowledge–is essential to create structures that become topological because of disorder, rather than despite it. This paradigm shifting approach is critical to finding materials that are only topological in amorphous form, precluding the inference from crystalline structures, and has far-reaching implications for future microelectronics. The goal of this project is to establish a relationship between structural and chemical short-range order and electronic and magnetic properties of amorphous Fe-(Tb,Mn)-Ge films through coordinated experimental studies using evaporation, magnetometry, magneto-transport, spectroscopies, and optical, x-ray, and electron microscopies. Tuning growth conditions (temperature, rate, composition, film thickness, seed layer, capping layer) and post-growth strain and curvature engineering enable the principal investigator to corroborate or refute the following three hypotheses: (1) Magnetic exchange and spin-orbit coupling are larger in amorphous structures than in their crystalline counterparts benefiting topological magnetism in films on membranes; (2) Adding Tb and Mn to iron germanium enhances spin frustration and magneto-resistance and yields smaller topological states at higher and lower temperatures, respectively; and (3) Strain and curvature allow for tailoring exchange, spin frustration, and magnetic order, including the magnetoelasticity-mediated voltage control of topological states. This project is jointly funded by Condensed Matter Physics Program, the Established Program to Stimulate Competitive Research (EPSCoR), and MPS Office of Strategic Initiatives. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.