Magnetic tunnel junctions and spin currents in modern computing

Abstract Electronic tunneling is a fundamentally quantum mechanical phenomenon. In a magnetic tunnel junction (MTJ), the tunnel conductance is further dependent on the electron’s spin state, adding another degree of freedom and leading to spin orientation-dependent tunnel resistance—known as tunnel magnetoresistance (TMR). In addition to the charge current, a spin-polarized tunnel current carries spin angular momentum flow. These two unique attributes, spin-dependent magnetoresistance and spin-current flow, bring a nano-MTJ capable of performing both read and write operations in a charge current-controlled environment, such as in integrated complimentary metal-oxide semiconductor (CMOS) technology for computing. In this article, I review some of the basic concepts involved in an MTJ for its TMR and for its spin current-related spin-transfer-torque (STT) switching, and some of the lessons learned over the course of developing STT-switched MTJs for CMOS-integrated memory as a commercial technology.