Quantitative magnetic imaging at the nanometer scale by ballistic electron magnetic microscopy

TL;DR

This paper demonstrates quantitative ballistic electron magnetic microscopy (BEMM) imaging of epitaxial Fe(001) nanostructures, enabling detailed magnetic configuration analysis and observing domain reversals, advancing nanoscale magnetic imaging techniques.

Contribution

The study introduces a method combining in situ nanostencil patterning with BEMM to quantitatively image magnetic states in epitaxial Fe nanostructures with high sensitivity.

Findings

High sensitivity imaging of magnetic configurations in Fe nanostructures.

Quantitative agreement between simulated and experimental BEMM images.

Observation of magnetic domain reversals under high current pulses.

Abstract

We demonstrate quantitative ballistic electron magnetic microscopy (BEMM) imaging of simple model Fe(001) nanostructures. We use in situ nanostencil shadow mask resistless patterning combined with molecular beam epitaxy deposition to prepare under ultra-high vacuum conditions nanostructured epitaxial Fe/Au/Fe/GaAs(001) spin-valves. In this epitaxial system, the magnetization of the bottom Fe/GaAs(001) electrode is parallel to the [110] direction, defining accurately the analysis direction for the BEMM experiments. The large hot-electron magnetoresistance of the Fe/Au/Fe/GaAs(001) epitaxial spin-valve allows us to image various stable magnetic configurations on the as-grown Fe(001) microstructures with a high sensitivity, even for small misalignments of both magnetic electrodes. The angular dependence of the hot-electron magnetocurrent is used to convert magnetization maps calculated by micromagnetic simulations into simulated BEMM images. The calculated BEMM images and magnetization rotation profiles show quantitative agreement with experiments and allow us to investigate the magnetic phase diagram of these model Fe(001) microstructures. Finally, magnetic domain reversals are observed under high current density pulses. This opens the way for further BEMM investigations of current-induced magnetization dynamics.