First Principle Study of Spin Tunneling Current Under Field Effect in Magnetic Tunnel Junction for Possible Application in STT-RAM

Abstract

A first principle analysis of Fe/MgO/Fe magnetic tunnel junction (MTJ) having gate voltage over insulated barrier region (MgO) is presented. Because of different work functions of gate and barrier materials, transfer of density of states (DOS) in forbidden energy gap of MgO is found above Fermi energy due to Schottky effect. It is reported that diffused DOS allows high tunneling of majority channel current because of less interference of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Delta _{{1}}}$ </tex-math></inline-formula> symmetry of Bloch states with evanescent states in barrier. It shows high spin injection efficiency 0.9928, 0.9959, and 0.9871 with tunnel magneto resistance (TMR) ratios 1743.30%, 1450.06%, and 572.62% at gate voltages 1–3 V, respectively, with left and right electrodes at 0.5 V. Present work gives a basis for using MTJs as three terminal devices in magnetic random access memory (MRAM) applications.