Non-uniform Superlattice Magnetic Tunnel Junctions

TL;DR

This paper introduces non-uniform superlattice magnetic tunnel junctions (Nu-SLTJs) with various profiles that significantly enhance TMR and reduce switching bias, enabling ultra-fast spin transfer torque switching for advanced spintronic devices.

Contribution

It proposes a new class of Nu-SLTJs with tailored profiles, demonstrating enhanced TMR, reduced switching bias, and rapid switching capabilities through atomistic simulations.

Findings

TMR enhancement to approximately 10^4-10^6%

Switching bias reduced by about 9 times

Achieves spin transfer torque switching in a few hundred picoseconds

Abstract

We propose a new class of non-uniform superlattice magnetic tunnel junctions (Nu-SLTJs) with the Linear, Gaussian, Lorentzian, and P\"oschl-teller width and height based profiles manifesting a sizable enhancement in the TMR($\approx 10^4-10^6\%$) with a significant suppression in the switching bias($\approx$9 folds) owing to the physics of broad-band spin filtering. By exploring the negative differential resistance region in the current-voltage characteristics of the various Nu-SLTJs, we predict the Nu-SLTJs offer the fastest spin transfer torque switching in the order of a few hundred picoseconds. We self-consistently employ the atomistic non-equilibrium Green's function formalism coupled with the Landau-Lifshitz-Gilbert-Slonczewski equation to evaluate the device performance of the various Nu-SLTJs. We also present the design of minimal three-barrier Nu-SLTJs having significant TMR($\approx 10^4\%$) and large spin current for ease of device fabrication. We hope that the class of Nu-SLTJs proposed in this work may lay the bedrock to embark on the exhilarating voyage of exploring various non-uniform superlattices for the next generation of spintronic devices.