Magnetization reversal and enhanced tunnel magnetoresistance ratio in perpendicular magnetic tunnel junctions based on exchange spring electrodes

• Published in: Journal of applied physics 2013-04, Vol.113 (13)
• Main Authors: Wang, Yi, Yin, Xiaolu, Le Roy, D., Jiang, Jun, Wei, H. X., Liou, S. H., Han, X. F.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4798507

The [Co/Pt]n multilayer based perpendicular magnetic tunnel junction stacks with wedged Co60Fe20B20 insertions up to 2 nm, and corresponding perpendicular magnetic tunnel junctions were magnetically and electrically investigated. The focus is on the influence of CoFeB insertions in the free and reference electrodes on the overall junction magnetization reversal and magnetoresistance response. The exchange spring behavior was revealed as the Co60Fe20B20 spins canting towards the in-plane direction in the [Co/Pt]n/Co60Fe20B20 hard/soft perpendicular magnetic electrodes. The broad range thickness of wedged Co60Fe20B20 insertion enables to reveal the critical transition, in particular, from rigid coupling to exchange spring coupling. With the help of 375°C annealing under 10 kOe magnetic field, the recovery from distinct multi-domain structure to nearly single domain structure was distinctly observed in the unpatterned perpendicular magnetic tunnel junction (p-MTJ) films with CoFeB thickness tCFB≥1.5 nm. Meanwhile, for the corresponding patterned perpendicular magnetic tunnel junctions with AlOx barrier, the tunnel magnetoresistance (TMR) ratio exhibited an intense enhancement over 100%. The TMR results and spin configurations were illustrated using an exchange spring model in both magnetic electrodes. The presented study shows the benefit of using exchange spring magnetic electrodes in perpendicular magnetic tunnel junction on their performance.