Characterization of (Pt[sub 2 nm]/Co[sub 0.4 nm])[sub 3]/Pt[sub x]/IrMn[sub 7 nm] multilayers by tomographic atom probe: On the role of a Pt spacer

Structural investigation of Ta3 nm/[(Pt2 nm/Co0.4 nm)3/Ptx/IrMn7 nm]7/Pt10 nm multilayers without (x = 0 nm) and with (x = 0.4 nm) a Pt spacer has been performed by laser-assisted tomographic atom probe. Without a Pt spacer a strong intermixing is observed at the Co/IrMn interface. In the multilayer containing a Pt spacer the Co/Pt/IrMn interface is very weakly intermixed. It thus appears that the Pt spacer acts as a diffusion barrier that prevents the Ir and Mn atoms from diffusing into the Co layer. The consequences of this effect on the magnetic properties are discussed. The exchange bias field and the anisotropy direction of these two multilayers are analyzed and correlated with the structural investigation.