Spin-Valley-Mismatched Altermagnet for Giant Tunneling Magnetoresistance

TL;DR

This paper develops a theoretical model for altermagnet-based heterojunctions, predicting giant tunneling magnetoresistance and verifying it through first-principles calculations, suggesting potential for ultra-high-density memory devices.

Contribution

It introduces a spin-transport theory incorporating transverse-wavevector-dependent spin polarization for altermagnets, enabling accurate prediction of giant TMR effects.

Findings

Predicts magnetoresistance exceeding 7.57×10^7% in KV2Se2O-based junctions.

Verifies the theory with first-principles calculations showing robustness against bias and spacer thickness.

Proposes KV2Se2O/MgO/KV2Se2O as a promising material system for room-temperature non-volatile memory.

Abstract

Altermagnet-based heterojunctions have demonstrated magnetoresistive effects in experiments, however, a predictive theoretical model for non-ferromagnetic structures has remained elusive. In this work, we develop a tunneling-based spin-transport theory that explicitly incorporates the transverse-wavevector ($\bf{k}_\|$)-dependent spin polarization of an altermagnet's transport channels, enabling the prediction of giant tunneling magnetoresistance (TMR). Based on the theory, we predict that the altermagnet KV$_2$Se$_2$O can reach the extreme limit of magnetoresistance. By performing first-principles transport calculations, we verify that magnetic tunnel junctions using the metallic KV$_2$Se$_2$O as the electrodes and few-layer MgO as the spacer exhibit zero-bias magnetoresistance larger than $7.57\times10^7$\%, which is robust against the bias and thickness of the spacer. Our research provides a quantitative design principle for next-generation spin-electronic devices and establishes KV$_2$Se$_2$O/MgO/KV$_2$Se$_2$O as a leading candidate material system for room-temperature ultra-high-density non-volatile memory.