Temperature stability of (Pt/Co)3/IrMn multilayers

The effect of annealing on the structural stability of (Pt-2nm/Co-0.4 (nm))(3)/IrMn7nm multilayers has been investigated using atom probe tomography. The composition of individual layers was measured after annealing at 300, 400, 500, and 700 degrees C. While results show that the (Pt/Co)(3)/IrMn stacking sequence is preserved up to 400 degrees C, there is an almost complete destruction of the multilayered structure when annealing at higher temperatures (500 and 700 degrees C). Co layers no more alternate with Pt-rich layers. The whole stack is transformed into an IrCo/PtMn bilayer. These results are interpreted on the basis of atomic mobilities and chemical affinities. Diffusion of Co and Mn is shown to become important when annealing temperature approaches 500 degrees C. Results are well accounted for by thermodynamics arguments considering the Co-Ir and Pt-Mn phase diagrams. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4745033]