Perpendicular magnetic tunnel junctions based on half-metallic NiCo₂O₄

Spin polarization and magnetic anisotropy are key properties that determine the performance of magnetic tunnel junctions (MTJs), which are utilized in various spintronic devices. Although materials that have both high spin polarization and sufficient perpendicular magnetic anisotropy are desirable for further developments of MTJs, such materials are rare because electronic structures necessary for achieving these two properties are distinct. Here, we experimentally show the inverse spinel ferrimagnet NiCo₂O₄ (NCO), whose band structure is theoretically predicted to be half-metallic, has both high spin polarization and perpendicular magnetic anisotropy. Perpendicular MTJs with NCO magnetic electrodes exhibit magnetoresistance up to 230%, indicating that the spin polarization of perpendicularly magnetized NCO is as high as −73%. Our experimental results demonstrate the potential of NCO as a half-metal with perpendicular magnetic anisotropy, which will lead to new paradigms for designing and developing all-oxide spintronic devices.