Magnetic coherent tunnel junctions with periodic grating barrier

TL;DR

This paper introduces a new theory for magnetic tunnel junctions with periodic barriers, explaining TMR oscillations and suggesting ways to enhance TMR towards infinity, applicable to layered materials and scalable fabrication.

Contribution

It develops a diffraction-based spintronic theory for MTJs with single-crystal barriers, addressing key TMR phenomena and proposing a scalable, layered-material-compatible design.

Findings

Explains TMR oscillations with barrier thickness.

Shows TMR can be enhanced towards infinity.

Proposes a scalable fabrication method for future MTJs.

Abstract

A new spintronic theory has been developed for the magnetic tunnel junction (MTJ) with single-crystal barrier. The barrier will be treated as a diffraction grating with intralayer periodicity, the diffracted waves of tunneling electrons thus contain strong coherence, both in charge and especially in spin. The theory can answer the two basic problems present in MgO-based MTJs: (1) Why does the tunneling magnetoresistance (TMR) oscillate with the barrier thickness? (2) Why is the TMR still far away from infinity when the two electrodes are both half-metallic? Other principal features of TMR can also be explained and reproduced by the present work. It also provides possible ways to modulate the oscillation of TMR, and to enhance TMR so that it can tend to infinity. Within the theory, the barrier, as a periodic diffraction grating, can get rid of the confinement in width, it can vary from nanoscale to microscale. Based on those results, a future-generation MTJ is proposed where the three pieces can be fabricated separately and then assembled together, it is especially appropriate for the layered materials, e.g., MoS2 and graphite, and most feasible for industries.