All-Altermagnetic Tunnel Junction of RuO2/NiF2/RuO2

Abstract: Emerging altermagnets offer a promising avenue for spintronics, yet their integration into magnetic tunnel junctions has been hindered by reliance on ferromagnetic electrodes (introducing stray fields) or limited functionality (non-tunable magnetoresistance without spin filtering). Here, we propose an all-altermagnetic tunnel junction (AAMTJ) paradigm composed exclusively of altermagnets-exemplified by experiment-feasible RuO2/NiF2/RuO2. Giant tunneling magnetoresistance of 11704%, and high spin-filtering of ~90% in both spin channels are achieved. This architecture unlocks tunable multistate magnetoresistance and spin filtering via magnetization control of electrode and barrier, stemming from their synergistic and antagonistic alignments of momentum-dependent altermagnetic spin-splitting. Our AAMTJ inherently exhibits low consumption and no stray field, with nonrelativistic spin splitting and zero magnetic moment, combining advantages of both ferromagnetic and antiferromagnetic tunnel junctions. This AAMTJ paradigm provides a realistically versatile platform to develop revolutionarily potential of altermagnets for reconfigurable magnetic memory devices.