Interfacial Resonance States-Induced Negative Tunneling Magneto-Resistance in Orthogonally Magnetized CoFeB/MgO/CoFeB

Magnetic tunnel junctions (MTJs) are essential for non-volatile magneto-resistive random access memory (MRAM) applications. Here, we report the observation of a negative tunneling magneto-resistance (TMR) in the CoFeB/MgO/CoFeB system with an orthogonally magnetized configuration. Through the modulation of the MgO thickness, the negative TMR component is up to 20% under a large negative voltage bias. Moreover, the tunneling anisotropic magneto-resistance (TAMR) measurements unveil that the negative TMR component likely arises from the interfacial resonance states (IRSs) in the minority band of the bottom ferromagnetic layer. Complementary first-principle calculations further quantify the IRS location and strength with respect to the Fermi-level position. Our work not only confirms the vital role of IRS in the electrical transport of MTJ but also provides valuable insights for the design of new-generation voltage-controlled MRAM and related spintronic applications.