Resonant tunneling driven spin torque enhancement in magnetic tunnel junctions: A DFT-NEGF simulation study

Abstract

We explore the potential improvements in the efficiency of magnetic tunnel junctions (MTJs) through the utilization of resonant tunneling in a quantum well-MTJ (qw-MTJ) with a non-magnetic metallic spacer (tungsten). Using the non-equilibrium Green’s function formalism with density functional theory, we calculate and analyze the conductivity of three different configurations of this structure with varying spacer widths, along with a comparison to a control configuration without the quantum well (0-W). Through the implementation of this novel configuration, we achieve a substantial enhancement in tunneling magnetoresistance, from 1420% in 0-W MTJ to 9900% in the trilayer-tungsten (3-W) qw-MTJ, accompanied by a 60× decrease in the resistance-area product, indicating a notable boost in current density. Additionally, our calculations of the spin transfer torque (STT) reveal a significant increase in its value compared to the control device, with the STT values rising for each tungsten width—from 6 μeV/V in the traditional MTJ to 470 μeV/V in the 3-W qw-MTJ. Furthermore, the critical voltage required for switching is reduced significantly from 137 mV in the 0-W t-MTJ to as low as 2.02 mV in the 3-W qw-MTJ (a 70× decrease), while the critical current remains nearly constant. This also results in a dramatic reduction in critical switching power, from 38.36 to 0.66 pW (a 60× decrease).