Effect of electrode composition on the tunnel magnetoresistance of pseudo-spin-valve magnetic tunnel junction with a MgO tunnel barrier

The authors investigate the effect of electrode composition on the tunnel magnetoresistance (TMR) ratio of (CoxFe100−x)80B20∕MgO∕(CoxFe100−x)80B20 pseudo-spin-valve magnetic tunnel junctions (MTJs). TMR ratio is found to strongly depend on the composition and thicknesses of CoFeB. High resolution transmission electron microscopy shows that the crystallization process of CoFeB during annealing depends on the composition and the thicknesses of the CoFeB film, resulting in different TMR ratios. A TMR ratio of 500% at room temperature and of 1010% at 5K are observed in a MTJ having 4.3nm and 4-nm-thick (Co25Fe75)80B20 electrodes with a 2.1-nm-thick MgO barrier annealed at 475°C.