Tunneling Magnetoresistance in Altermagnetic RuO2-Based Magnetic Tunnel Junctions

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 Letter, we demonstrate spin-dependent tunneling magnetoresistance (TMR) in RuO_{2}-based magnetic tunnel junctions, which suggests the spin-splitted anisotropic band structure of our RuO_{2} films. The observed TMR is contingent on the direction of the Néel vector of RuO_{2} and reverse its sign by the inversion of the Néel vector. 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.