Axel Lubk

First-principles study of ferroelectric domain walls in multiferroic bismuth ferrite

We present a first-principles density-functional study of the structural, electronic, and magnetic properties of the ferroelectric domain walls in multiferroic

Nanoscale three-dimensional reconstruction of electric and magnetic stray fields around nanowires

{\text{BiFeO}}_{3}

Exploiting lens aberrations to create electron-vortex beams.

. We find that domain walls in which the rotations of the oxygen octahedra do not change their phase when the polarization reorients are the most favorable and of these, the

Weighted simultaneous iterative reconstruction technique for single-axis tomography

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Electron holography for fields in solids: problems and progress.

domain wall centered around the BiO plane has the lowest energy. The

Transport of intensity phase retrieval of arbitrary wave fields including vortices.

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Topological analysis of paraxially scattered electron vortex beams

and

Retro-fitting an older (S)TEM with two Cs aberration correctors for 80 kV and 60 kV operation

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Noise estimation for off-axis electron holography

walls have a significant change in the component of their polarization perpendicular to the wall; the corresponding step in the electrostatic potential is consistent with a recent report of electrical conductivity at the domain walls. Finally, we show that changes in the Fe-O-Fe bond angles at the domain walls cause changes in the canting of the Fe magnetic moments which can enhance the local magnetization at the domain walls.

Shaping electron beams for the generation of innovative measurements in the (S)TEM

Static electromagnetic stray fields around nanowires (NWs) are characteristic for a number of important physical effects such as field emission or magnetic force microscopy. Consequently, an accurate characterization of these fields is of high interest and electron holographic tomography (EHT) is unique in providing tomographic 3D reconstructions at nm spatial resolution. However, several limitations of the experimental setup and the specimen itself are influencing EHT. Here, we show how a deliberate restriction of the tomographic reconstruction to the exterior of the NWs can be used to mitigate these limitations facilitating a quantitative 3D tomographic reconstruction of static electromagnetic stray fields at the nanoscale. As an example, we reconstruct the electrostatic stray field around a GaAs-AlGaAs core shell NW and the magnetic stray field around a Co2FeGa Heusler compound NW.