Regensburg 2000 – scientific programme

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AM: Magnetismus

AM 18: Magnetowiderstand II: Oxide und Tunnelmagnetowiderstand

AM 18.10: Talk

Thursday, March 30, 2000, 11:45–12:00, H10

Apparent spin polarization decay in Cu dusted Co/Al₂O₃/Co tunnel junctions — •Patrick LeClair, Henk Swagten, Jürgen Kohlhepp, Rene van de Veerdonk, and Wim de Jonge — Department of Applied Physics, Eindhoven University of Technology, The Netherlands

Co/Al₂O₃/Co magnetic tunnel junctions with an interfacial Cu layer have been investigated via in-situ X-Ray Photoelectron Spectroscopy, Auger Electron Spectroscopy, and Scanning Tunneling Microscopy as well as ex-situ magnetotransport measurements. In identically grown structures, Cu interlayers grown on Co give an exponential decay of the tunneling magnetoresistance (TMR) with ξ≈0.26nm while Cu grown on Al₂O₃ has a much longer decay length of 0.70nm. The difference in decay lengths can be explained by differing growth morphologies in the two cases, as monitored by the in-situ spectroscopies, and in this way clarifies the present disagreement in literature. For monolayer coverage of Cu, for the first time we show that tunneling spin polarization is suppressed by at least a factor of 2 compared to Co. At 2ML the tunneling spin polarization is suppressed by more than a factor of 5, while beyond approximately 5ML it becomes vanishingly small.