Tunneling magnetoresistance in altermagnetic RuO${}_2$-based magnetic tunnel junctions

Abstract

Altermagnets exhibit characteristics akin to antiferromagnets, with spin-split anisotropic bands in momentum space. RuO${}_2$ has been considered as a prototype altermagnet; however, recent reports have questioned altermagnetic ground state in this material. In this study, we provide direct experimental evidence of altermagnetic characteristics in RuO${}_2$ films by demonstrating spin-dependent tunneling magnetoresistance (TMR) in RuO${}_2$-based magnetic tunnel junctions. Our results show the spin-splitted anisotropic band structure of RuO${}_2$, with the observed TMR determined by the direction of the Néel vector of RuO${}_2$. These results reflect the altermagnetic nature of RuO${}_2$ and highlight its potential for spintronic applications, leveraging the combined strengths of ferromagnetic and antiferromagnetic systems.