Regensburg 2013 – wissenschaftliches Programm

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MI: Fachverband Mikrosonden

MI 2: Topical Session: Using Transmission Electron Microscopy to Unravel the Mysteries of Materials II - Joint Session with MM

MI 2.1: Hauptvortrag

Montag, 11. März 2013, 11:45–12:15, H4

Prospects for mapping spins with atomic resolution in TEM — •Johan Verbeeck — EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium

In this talk, the prospects for mapping spins with atomic resolution in a TEM will be outlined. The proposed method is based on the use of electron vortex STEM probes. Such probes contain a helical phase of the type ψ(r,φ)=f(r) e^{i m φ} with m the so-called topological charge. This topological charge is responsible for an orbital angular momentum of mℏ and a magnetic moment of mµ_B carried by the electron probe. The phase symmetry affects the dipole selection rules in inelastic scattering which allows us to measure the change in magnetic quantum number upon excitation. As vortex electron probes can now be made to atomic size, we also expect to get magnetic information from individual atom columns in atomic resolution STEM-EELS experiment. Indeed, simulations show that even for thicker samples where multiple scattering can become important, an atomic resolution signal remains that contains information on the spin and orbital magnetic moment of a targeted atom with atomic resolution. Preliminary experiments are shown and the different experimental obstacles will be discussed.