Mid-Term Report Summary - IMAGINE (Imaging Magnetism in Nanostructures using Electron Holography)
This project aims to develop an advanced characterization methodology based on electron holography that allows quantitative information about magnetic spin structures in nanocrystals that have sizes of below 20 nm to be obtained in the transmission electron microscope. The specific scientific objectives are to achieve a detection limit of 100 Bohr magnetons or better for measuring the magnetic moments of individual nanocrystals, a spatial resolution of 0.5 nm or better for magnetic field measurement, an experimental approach for measuring three-dimensional magnetic vector fields in nanocrystals, direct imaging of magnetization reversal processes in 2-20 nm nanoparticles as a function of temperature and comparisons of electron holographic measurements with structural characterization and micromagnetic models.
Key experimental achievements have included the quantitative mapping of dipolar magnetism in two-dimensional arrays of 10 nm Co nanoparticles, temperature-dependent magnetism in 100 nm magnetite nanocrystals in minerals, studies of the influence of oxidation on the magnetic microstructure of individual magnetite nanocrystals, the mapping of magnetic states in novel magnetic gyroid structures, magnetic nanotubes, defective and elongated biogenic magnetite nanocrystals and electrodeposited magnetic nanowires with different magnetic underlayers. Experiments that are in progress include studies of the temperature and magnetic field dependence and geometric confinement of skyrmions in nanofabricated structures and thin films, the application of both field cooling and zero field cooling to individual magnetic nanostructures in situ in the transmission electron microscope and mapping of the magnetic fields of electrical currents in nanoscale circuits
Methodological progress includes the development of new algorithms and software for model-based vector field tomography, the demonstration of 0.5 nm spatial resolution for electron holography in magnetic-field-free conditions, the development of high-frequency double-exposure electron holography for ultrafast studies of magnetic switching processes, comparisons of maps of magnetic microstructure in individual magnetic nanocrystals obtained using the complementary techniques of off-axis electron holography and electron magnetic chiral dichroism and experiments aimed at shaping electron beams using magnetic and electric fields, phase and amplitude masks and hardware aberration correctors and their application to the characterisation of magnetic properties in materials. Instrumental developments include novel in-plane-magnetizing and high-frequency specimen holders for magnetic switching studies and the use of new hardware to achieve ultra-fast electron tomography combined with off-axis electron holography for the sub-10-s acquisition of full tomographic tilt series of electron holograms for studies of dynamic magnetic processes in materials.
Riese, Gelinde (Administrative Officer Technology Transfer)
SubjectsPhysical sciences and engineering
Record Number: 183503 / Last updated on: 2016-06-16
Information source: SESAM