Tunneling magnetoresistance in altermagnetic tunnel junctions with the half-metal electrode

As a critical component of high-efficiency and low-power memory devices, the development of magnetic tunnel junctions (MTJs) with large tunneling magnetoresistance (TMR) is highly demanded. Altermagnets, a particular magnetic system, with zero net magnetizations and non-spin-degenerate conductance due to momentum-dependent spin polarization, can generate TMR when used to replace ferromagnetic and traditional antiferromagnetic electrodes. In this study, we present a ferromagnet/insulator barrier/altermagnet junction that exhibits large intrinsic TMR. In this system, the ferromagnetic electrode is a half-metallic alloy with a unidirectional Fermi surface. We demonstrate that a large TMR can be obtained in V0.5Cr0.5O2/TiO2/RuO2 through first-principles calculations and quantum transport calculations. However, the TMR ratio is almost zero when the ferromagnetic electrode is replaced with pristine VO2 or CrO2. This behavior can be attributed to the unidirectional conduction channel rather than transport direction. Our work presents an efficient approach to realize large TMR ratio in ferromagnet/insulator barrier/altermagnet MTJs, which could contribute to the potential development of altermagnet-based spintronic devices.