  Magnetic tunneling junctions (MTJs) are essential for non-volatile
magneto-resistive random access memory (MRAM) applications. Here, we report the
observation of a large negative tunneling magneto-resistance (TMR) in the
CoFeB/MgO/CoFeB system with an orthogonally-magnetized configuration. Through
the thickness modulation of the MgO barrier, the negative TMR component can be
enhanced up to 20% under a negative voltage bias. Moreover, the tunnel
anisotropic magneto-resistance measurements unveil that the negative TMR
component likely arises from the interfacial resonance states (IRS) 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 confirm the vital role of IRS in the
electrical transport of MTJ, but also provide valuable insights for the design
of new-generation voltage-controlled MRAM and related spintronic applications.
