Room temperature chiral magnetic skyrmion in ultrathin magnetic nanostructures

Magnetic skyrmions are chiral spin structures with a whirling configuration. Their topological properties, nanometer size and the fact that they can be moved by small current densities have opened a new paradigm for the manipulation of magnetisation at the nanoscale. To date, chiral skyrmion structures have been experimentally demonstrated only in bulk materials and in epitaxial ultrathin films and under external magnetic field or at low temperature. Here, we report on the observation of stable skyrmions in sputtered ultrathin Pt/Co/MgO nanostructures, at room temperature and zero applied magnetic field. We use high lateral resolution X-ray magnetic circular dichroism microscopy to image their chiral N\'eel internal structure which we explain as due to the large strength of the Dzyaloshinskii-Moriya interaction as revealed by spin wave spectroscopy measurements. Our results are substantiated by micromagnetic simulations and numerical models, which allow the identification of the physical mechanisms governing the size and stability of the skyrmions.Comment: Submitted version. Extended version to appear in Nature Nanotechnolog

Imaging at the mesoscale (leem, peem)

1noThe capability to display images containing chemical, magnetic, and structural information and to perform spectroscopy and diffraction from a μm-sized area makes cathode lens electron microscopy one of the most used and reliable techniques to analyze surfaces at the mesoscale. Thanks to its versatility, LEEMlow-energyelectron microscopy (LEEM)/PEEM systems are currently employed to study model systems in the fields of nanotechnology, nanomagnetism, material science, catalysis, energy storage, thin films, and 2-D (two-dimensional) materials. In this chapter, we will present a brief but complete review of this class of instruments. After a historical digression in the introductory section, we will first show the basic operating principles of a simple setup and then the elements that can be added to improve performance. Later, two sections will be dedicated to LEEM and PEEMphotoelectronemission microscopy (PEEM), respectively. In both cases, a theoretical discussion on the contrast mechanisms will prelude to a showcase of the operating modes of the instrument, with clear examples that will show the best performance available today. Finally, a brief discussion about the future developments of cathode lens electron microscopy will close the chapter.reservedmixedSala A.Sala, A