High-sensitivity mapping of magnetic induction fields with nanometer-scale resolution: comparison of off-axis electron holography and pixelated differential phase contrast

TL;DR

This paper compares off-axis electron holography and pixelated differential phase contrast in TEM to measure magnetic fields at nanometer resolution, highlighting their respective sensitivities and spatial resolutions.

Contribution

It provides a direct comparison of two advanced TEM techniques for magnetic field mapping, demonstrating the advantages of pixelated STEM in sensitivity.

Findings

Pixelated STEM offers higher sensitivity than electron holography.

Electron holography achieves better spatial resolution.

Both techniques are effective for high-resolution magnetic field mapping.

Abstract

We compare two transmission electron microscopy (TEM) based techniques that can provide highly spatially resolved quantitative measurements of magnetic induction fields at high sensitivity. To this end, the magnetic induction of a ferromagnetic NiFe nanowire has been measured and compared to micromagnetic modelling. State-of-the-art electron holography has been performed using the averaging of large series of holograms to improve the sensitivity of the measurements. These results are then compared those obtained from pixelated (or 4D) scanning transmission electron microscopy (STEM). This emerging technique uses a pixelated detector to image the local diffraction patterns as the beam is scanned over the sample. For each diffraction pattern, the deflection of the beam is measured and converted into magnetic induction, while scanning the beam allows to build a map. Aberration corrected Lorentz (field-free) configurations of the TEM and STEM were used for an improved spatial resolution. We show that the pixelated STEM approach, even when performed using an old generation of charge-coupled device camera, provides better sensitivity at the expense of spatial resolution. A more general comparison of the two techniques is given.