Spin-transfer torque switching below 20 kA/cm$^2$ in perpendicular magnetic tunnel junctions

TL;DR

This paper reports the achievement of ultra-low critical spin-transfer torque switching currents below 20 kA/cm$^2$ in perpendicular magnetic tunnel junctions, advancing the potential for energy-efficient spintronic devices.

Contribution

It demonstrates a significant reduction in switching currents through optimization of bias fields in Co-Fe-B/MgO MTJs with perpendicular anisotropy, enabling new experimental possibilities.

Findings

Critical switching current densities below 20 kA/cm$^2$ achieved

TMR ratios up to 64% at 4 ML barrier thickness

Potential for thermally driven spin-transfer torque studies

Abstract

We demonstrate the reduction of critical spin-transfer torque (STT) switching currents in Co-Fe-B/MgO based magnetic tunnel junctions (MTJ) with perpendicular magnetization anisotropy (PMA). The junctions yield tunnel magnetoresistance (TMR) ratios of up to 64% at 4 monolayer (ML) tunnel barrier thickness. In this paper, the reduction of the critical switching current density is studied. By optimizing the applied bias field during DC-STT measurements, ultra low critical switching current densities of less than 20 kA/cm$^2$, even down to 9 kA/cm$^2$, are found. With the reduced switching currents, our samples are ideal candidates for further experimental studies such as the theoretical predicted thermally driven spin-transfer torque effect.