Regensburg 2019 – wissenschaftliches Programm
SYGT 1.3: Hauptvortrag
Dienstag, 2. April 2019, 10:30–11:00, H1
Magnetization configurations and reversal of individual ferromagnetic nanotubes — •Martino Poggio — Department of Physics, University of Basel, Basel, Switzerland
Due to their high surface-to-volume ratio, equilibrium magnetization configurations and reversal processes in magnetic nanostructures are often dominated by the influence of surface and edge domains. As a result, surface imperfections and roughness can determine configurations and impede a controllable, reproducible, and fast reversal process. Nanomagnets in flux-closure magnetization configurations, however, are less sensitive to the shape of boundaries, since these configurations close magnetic flux lines within the magnet. Ferromagnetic nanotubes (FNTs), because of their core-free geometry, favor equilibrium flux-closure configurations with magnetization curling around their hollow core. In addition, reversal of a uniform magnetization in these structures has been predicted to nucleate and propagate through vortex domains. Here, we use three techniques to study the equilibrium configurations and reversal processes in individual FNTs: x-ray magnetic circular dichroism photo-emission electron microscopy, scanning nanometer-scale superconducting quantum interference device microscopy, and dynamic cantilever magnetometry. We find evidence for different types of remnant flux-closure configurations. We also observe the signatures of vortex-nucleated magnetization reversal in individual FNTs, as predicted by theory. These developments may have consequences for the design of nanomagnetic elements required for future high-density magnetic storage devices.