This project seeks to utilize chiral magnetic Skyrmion domains in nanowires of silicides and germanides for magnetic data storage applications. Skyrmions are a novel type of exotic magnetic ordering in which electron spins orient to form a topologically non-trivial whirlpool-like structure. They were recently discovered in non-centrosymmetric B20 monosilicides (MnSi, Fe1-xCoxSi) or monogermanide (FeGe). Skyrmions can be thought of as magnetic knots, quasi-particle-like domains that are stable to small perturbations in magnetic field and temperature and do not pin strongly to the crystal lattice or impurities. Skyrmions strongly couple to electrical currents due to the spin torque interaction therefore much lower critical current density is needed to drive the motion of Skyrmion domains. Skyrmions present novel opportunities for implementing spintronic and magnetic storage device designs. Furthermore, nanowires present an ideal system to realize, detect, and manipulate isolated chiral magnetic Skyrmions in the absence of an applied magnetic field due to the stabilization of the Skyrmion phase in confined one-dimensional geometry. Building on their progress in the growth of metal silicide and germanide nanowires and the expertise in spintronic device investigations using nanowire building blocks,PI plan to observe, measure, and manipulate chiral Skyrmions in nanowires of non-centrosymmetric B20 silicides, such as Fe1-xCoxSi and MnSi. Specifically, through an international collaboration with the University of Tokyo, Lorentz transmission electron microscopy will be used to visualize Skyrmions in these nanowires. Furthermore, topological Hall effect due to Skyrmions will be electrically measured in nanowires. Finally, the emergent dynamics of Skyrmions and their motions will be investigated in nanowire electrical devices.
The intellectual merit: This research project presents the first opportunity for observing and electrically detecting Skyrmion motion by integrating existing nanowire materials with careful device and physical studies. Nanowire geometry has several advantages over thin film and bulk samples and is better suited for demonstrating such novel phenomenon therefore nanowires can serve as a model material platform that takes the study of Skyrmions from the fundamental physics and to more applied device work and eventual applications. Due to their unique and superior properties, Skyrmions have advantages over the conventional domain walls in metallic ferromagnets. The realization and electrical detection of ground state isolated Skyrmions in nanowires would demonstrate the proof-of-concept for utilizing Skyrmions for magnetic storage.
The broader impact of the project includes that the success of the project will open up new design concepts for magnetic memory and spintronic devices with low-power, enhanced performance, and mass data storage, therefore bringing broad technological impacts. Education and outreach is closely integrated with active research in this project by recruiting underrepresented undergraduate students to participate in nanotechnology research in spintronic materials and devices, and by further developing a nanotechnology workshop for high school students and teachers. Used computer hard drives and integrated circuit chips will be examined during the workshop to allow students to learn basic concepts in spintronics and nanoelectrics and how they connect to digital gadgets, encouraging their interest in science and engineering.
