Search for alternative magnetic tunnel junctions based on all-Heusler stacks

TL;DR

This study proposes Fe3Al/BiF3/Fe3Al as a promising alternative to traditional magnetic tunnel junctions, achieving high tunneling magneto-resistance and voltage resilience through structural compatibility and spin gap properties.

Contribution

It introduces a novel all-Heusler stack with superior TMR performance and voltage stability, expanding the materials options for high-performance magnetic tunnel junctions.

Findings

TMR exceeds 25,000% at low bias with <2nm barrier

The stack maintains high TMR under high voltages due to spin gap

Fe3Al/BiF3/Fe3Al is a viable alternative to FeCoB/MgO

Abstract

By imposing the constraints of structural compatibility, stability and a large tunneling magneto-resistance, we have identified the Fe$_3$Al/BiF$_3$/Fe$_3$Al stack as a possible alternative to the well-established FeCoB/MgO/FeCoB in the search for a novel materials platform for high-performance magnetic tunnel junctions. Various geometries of the Fe$_3$Al/BiF$_3$/Fe$_3$Al structure have been analyzed, demonstrating that a barrier of less than 2~nm yields a tunneling magneto-resistance in excess of 25,000~\% at low bias, without the need for the electrodes to be half-metallic. Importantly, the presence of a significant spin gap in Fe$_3$Al for states with $\Delta_1$ symmetry along the stack direction makes the TMR very resilient to high voltages.