Auger electron spectroscopy and Rutherford back-scattering spectroscopy were used to study the extent of interdiffusion during thermal treatment of pinned electrodes of magnetic tunneling junctions (Ta/NiFe/Cu/NiFe/IrMn/CoFe). The concentration profile results revealed a significant amount of Mn-CoFe interdiffusion when samples were annealed at 200 to 400C in a vacuum. The multilayer was completely intermixed at 400C. It was demonstrated that the migration of Mn was enhanced by preferential oxidation of the Mn at the surface. When a thin layer of Ta (for oxidation protection) was deposited on top of the electrode, Mn diffusion was minimal up to 300C. The results suggested that Mn diffusion could be enhanced by the presence of free O radicals.

Interdiffusion in Antiferromagnetic/Ferromagnetic Exchange Coupled NiFe/IrMn/CoFe Multiplayer. J.H.Lee, H.D.Jeong, C.S.Yoon, C.K.Kim, B.G.Park, T.D.Lee: Journal of Applied Physics, 2002, 91[3], 1431-5