Effect of field-annealing on magnetostriction and tunneling magnetoresistance of Co/AlOx/Co/IrMn junctions

The magnetostriction (λs) and tunneling magnetoresistance (TMR) of two Co/AlOx/Co/IrMn MTJ systems that were deposited on Si(1 0 0) and glass substrate were examined at RT and field-annealing with various thicknesses of AlOx. One structure was a Si(1 0 0)/Ta/Co/AlOx/Co/IrMn/Ta system, and the other was a glass/Co/AlOx/Co/IrMn system. The experimental results reveal that, in the Si(1 0 0)/Ta/Co/AlOx/Co/IrMn/Ta system, the ratio of TMR is maximal under the field-annealing condition, and is optimal at an AlOx thickness of 26 Å as well as in the RT condition. EDS analysis demonstrates that, these results are related to the distribution of Co and O atoms, because the oxidation of AlOx is most extensive at a thickness of 26 Å. In the glass/Co/AlOx/Co/IrMn system, λs does not significantly vary under the RT condition; however, λs is maximized (−20 ppm) by field-annealing at an AlOx thickness of 17 Å. The abundance of Co and O in the system dominates the behavior of λs, according to EDS analysis. Finally, the minimum value of λs and the maximum ratio of TMR are −8 ppm and 60%, respectively, at an AlOx thickness of 26 Å under the field-annealing condition.