All-Altermagnetic Tunnel Junction of RuO2/NiF2/RuO2

TL;DR

This paper introduces an all-altermagnetic tunnel junction using RuO2 and NiF2, achieving extremely high tunneling magnetoresistance and spin filtering efficiencies, enabling multistate high-performance spintronic devices without stray fields.

Contribution

The study proposes the first all-altermagnetic tunnel junction with experimentally feasible materials, demonstrating significantly higher magnetoresistance than traditional junctions and enabling tunable spin filtering.

Findings

Achieved tunneling magnetoresistance of over 11,700% with NiF2 barrier.

High spin filtering efficiency of approximately 90%.

High magnetoresistance maintained with TiO2 spacer.

Abstract

Emerging altermagnets with zero net magnetic moment and moment-dependent spin splitting offer a promising avenue for antiferromagnetic spintronic devices, yet their integration into magnetic tunnel junctions has been hindered by reliance on ferromagnetic electrodes (introducing stray fields) or by limited functionality (non-tunable magnetoresistance without spin filtering). Here, we propose an all-altermagnetic tunnel junction (AAMTJ) paradigm composed exclusively of altermagnets, exemplified by experimentally feasible RuO2/NiF2/RuO2. By introducing an altermagnetic NiF2 barrier, the achieved tunneling magnetoresistances of 11,704%, 2,496% and 1,892% for RuO2/NiF2/RuO2 are much higher than that of 221% for RuO2/TiO2/RuO2 with a nonmagnetic TiO2 barrier. High spin filtering efficiencies of ~90% are also obtained. This architecture unlocks multistate high magnetoresistance and spin filtering via magnetization control of the electrodes and barrier, stemming from their synergistic and antagonistic alignments of momentum-dependent altermagnetic spin-splitting. Importantly, high tunneling magnetoresistances are still achieved in the AAMTJ with TiO2 spacer of RuO2/TiO2/NiF2/TiO2/RuO2. Our AAMTJ inherently exhibits low consumption and zero stray field, with nonrelativistic spin splitting and vanishing magnetic moment, combining the advantages of both ferromagnetic and antiferromagnetic tunnel junctions. This AAMTJ paradigm opens an interesting avenue within the area of high-performance altermagnet-based tunnel junctions.