The extent of Mn diffusion to the plasma-oxidized AlOx tunnel barrier in the magnetic tunnel junctions was explored by using Rutherford back-scattering spectroscopy and Auger electron spectroscopy. A thin film stack consisting of Ta/AlOx/CoFe/IrMn/NiFe/Ta was deposited with the AlOx layer treated under different plasma oxidation durations. When the film stack was annealed at 300C, Rutherford back-scattering spectroscopy and Auger electron spectroscopy analysis showed that the Mn diffusion to the AlOx layer progressively increased as the tunnel barrier layer was over-oxidized. The Mn diffusion appeared to be enhanced and controlled by the presence of O near to the tunnel barrier, due to the relatively high O-affinity of Mn. This observation implicates that the oxidation condition of the tunnel barrier not only determines the as-deposited state of the junction, but also had a large bearing on the thermal stability of the exchange-biased tunnel junctions.

Mn Diffusion in Plasma Oxidized AlOx Insulation Layer in Magnetic Tunnel Junctions. J.H.Lee, C.S.Yoon, C.K.Kim, J.H.Yuh, Y.W.Kim: Journal of Applied Physics, 2002, 91[10], 7472-4