Giant tunneling magnetoresistance in altermagnetic heterostructures via multi-stage spin-filtering

Abstract

Altermagnets, which combine the advantages of ferromagnetic spin splitting and antiferromagnetic zero stray field, have been regarded as a promising platform for spintronic applications. However, it is challenging to achieve high tunneling magnetoresistance (TMR) in altermagnet-based tunnel junctions due to the momentum-dependent spin splitting. By leveraging the intrinsic spin-dependent tunneling asymmetry of altermagnetic (AM) insulators, we investigate spin-polarized transport properties in altermagnetic tunnel junctions (AMTJs) with fully altermagnetic heterostructure barriers using first-principles quantum-transport calculations. Specifically, we design and compare [110]-oriented heterostructured AMTJs composed of IrO²/CoF²/MF²/CoF²/IrO² (M = Fe, Mn) with a homogeneous CoF₂-barrier reference. Our results show that the FeF₂-based heterostructure achieves giant TMR ratios of up to 196,468%, while the MnF₂-based counterpart yields substantial values up to 2,322%, far exceeding the modest 14% obtained for the homogeneous CoF₂ barrier system. Mechanistically, this enhancement originates from a multi-stage spin-filtering effect enabled by the heterostructured barriers, which breaks the single transport-mode constraint of homogeneous barriers through the symmetry-selective superposition of spin states. These findings highlight the potential of staggered altermagnetic heterostructures to overcome the single-mode transport limitation of conventional MTJs, providing a robust pathway toward next-generation high-performance altermagnetic spintronic devices.

Keywords

altermagnet / tunnel junction / spin filtering / first-principles calculations

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Higher Education Press 2026

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