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

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 $\hat{I}{”}_1$ symmetry along the stack direction makes the TMR very resilient to high voltages.