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

TL;DR

This study demonstrates that interfacial resonance states can induce negative tunneling magneto-resistance in CoFeB/MgO/CoFeB magnetic tunnel junctions, with implications for voltage-controlled spintronic devices.

Contribution

It reveals the role of interfacial resonance states in negative TMR and shows how MgO thickness modulation enhances this effect, advancing MTJ design.

Findings

Negative TMR up to 20% observed under negative bias

Interfacial resonance states linked to negative TMR

First-principles calculations confirm IRS influence

Abstract

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.