Spin Transfer Switching and Spin Polarization in Magnetic Tunnel Junctions with Mgo and Alox Barriers

TL;DR

This paper reports on the improved spin transfer switching efficiency in MgO-based magnetic tunnel junctions, highlighting their higher tunneling spin polarization and lower switching current density compared to AlOx-based junctions.

Contribution

It demonstrates that MgO barriers significantly enhance spin transfer switching performance due to higher tunneling spin polarization, compared to AlOx barriers.

Findings

MgO-based MTJs have up to 150% TMR ratio.

Switching current density is 3-4 times lower in MgO MTJs.

TSP is higher in MgO (0.46) than in AlOx (0.22).

Abstract

We present spin transfer switching results for MgO based magnetic tunneling junctions (MTJs)with large tunneling magnetoresistance (TMR) ratio of up to 150% and low intrinsic switching current density of 2-3 x 10 MA/cm2. The switching data are compared to those obtained on similar MTJ nanostructures with AlOx barrier. It is observed that the switching current density for MgO based MTJs is 3-4 times smaller than that for AlOx based MTJs, and that can be attributed to higher tunneling spin polarization (TSP) in MgO based MTJs. In addition, we report a qualitative study of TSP for a set of samples, ranging from 0.22 for AlOx to 0.46 for MgO based MTJs, and that shows the TSP (at finite bias) responsible for the current-driven magnetization switching is suppressed as compared to zero-bias tunneling spin polarization determined from TMR.