Prospects for out-of-plane magnetic field measurements through interference of electron vortex modes in the TEM. (19th November 2019)

• Record Type: Journal Article
• Authors: Guzzinati, Giulio; Béché, Armand; McGrouther, Damien; Verbeeck, Jo
• Is Part Of: Journal of optics. Volume 21:Number 12(2019)
• Publication Date: 2019-11-19
• Subjects: rotational differential phase contrast (DPC) -- magnetometry -- 4DSTEM -- TEM -- electron vortex beams -- Aharanov–Bohm -- Zeeman shift; Optics -- Periodicals; 535.05
• DOI: 10.1088/2040-8986/ab51fc
• Languages: English
• ISSNs: 2040-8978

Abstract

Abstract: Magnetic field mapping in transmission electron microscopy is commonplace, but all conventional methods provide only a projection of the components of the magnetic induction perpendicular to the electron trajectory. Recent experimental advances with electron vortices have shown that it is possible to map the out of plane magnetic induction in a TEM setup via interferometry with a specifically prepared electron vortex state carrying high orbital angular momentum (OAM). The method relies on the Aharonov–Bohm phase shift that the electron undergoes when going through a longitudinal field. Here we show how the same effect naturally occurs for any electron wave function, which can always be described as a superposition of OAM modes. This leads to a clear connection between the occurrence of high-OAM partial waves and the amount of azimuthal rotation in the far field angular distribution of the beam. We show that out of plane magnetic field measurement can thus be obtained with a much simpler setup consisting of a ring-like aperture with azimuthal spokes. We demonstrate the experimental setup and explore the achievable sensitivity of the magnetic field measurement.