Effect of high annealing temperature on giant tunnel magnetoresistance ratio of CoFeB/MgO/CoFeB magnetic tunnel junctions

TL;DR

This study demonstrates that annealing CoFeB/MgO/CoFeB magnetic tunnel junctions at 450°C significantly enhances TMR ratios to near theoretical limits, with implications for spintronic device performance.

Contribution

It reveals the impact of high-temperature annealing on TMR ratios and elucidates the mechanisms affecting different MTJ structures.

Findings

TMR ratio reaches 472% at room temperature

Annealing at 450°C induces interdiffusion in EB-SV MTJs

High-temperature annealing approaches theoretical TMR limits

Abstract

We report tunnel magnetoresistance (TMR) ratios as high as 472% at room temperature and 804% at 5 K in pseudo-spin valve (SV) CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJs) annealed at 450oC, which is approaching the theoretically predicted value. By contrast, the TMR ratios for exchange-biased (EB) SV MTJs with a MnIr antiferromagnetic layer are found to drop when they are annealed at 450oC. Energy dispersive X-ray analysis shows that annealing at 450oC induces interdiffusion of Mn and Ru atoms into the MgO barrier and ferromagnetic layers in EB-SV MTJs. Mechanisms behind the different annealing behavior are discussed.