Effect of oxidation and annealing on tunnel barrier structure and composition in IrMn / CoFe / TiO x / CoFe magnetic tunnel junctions

The effects of oxidation time and annealing conditions on sputter-deposited magnetic tunnel junctions with a TiO x barrier have been investigated. High resolution electron microscopy showed that longer oxidation times led to a significant increase in barrier layer width and to the formation of large volumes of oxides of Co and Fe. Annealing promoted extensive diffusion of Mn to the barrier region and the oxidation of Mn to MnO x concurrent with the reduction in oxides of Co and Fe. Annealing also increased the peak oxygen content of the barrier region and resulted in a distinct asymmetry in the barrier oxide structure.