Dresden 2006 – scientific programme
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MA: Magnetismus
MA 3: Spin-Dependent Transport Phenomena I
MA 3.8: Talk
Monday, March 27, 2006, 12:00–12:15, HSZ 103
Tunneling Magneto Resistance in Co-Fe-B/Al-Ox Magnetic Tunnel Junctions — •Oliver Schebaum1, Andy Thomas1, Hubert Brückl2, and Günter Reiss1 — 1Bielefeld University, Nano Device Group, Universitätsstrasse 25, 33615 Bielefeld — 2ARCS research GmbH, Division "Nano System Technology", Tech Gate Vienna, Donau-City-Strasse 1, 1220 Vienna, Austria
We investigated the effect of Co-Fe-B as the free and the pinned magnetic layer in magnetic tunnel junctions (MTJs). The lower electrode was exchange-bias coupled to MnIr and Al-Ox was used as a tunnel barrier. The samples were prepared by dc/rf-magnetron sputtering in a UHV chamber with a base pressure of 1 × 10−7 mbar. The metallic Aluminum was oxidized utilizing electron cyclotron plasma oxidation in a pure Oxygen.
We measured the influence of different B compositions of the electrodes using sputter-targets with 5% and 12% of B [Co 70%/Fe 25%/B 5%; Co 62%/Fe 26%/B 12%]. Furthermore, we optimized the samples yielding high TMR ratios by varying the thickness of the Al-Ox barrier.
The TMR effect of the samples prepared with a 5% B target decreased (38% @ RT) compared with standard MTJs consisting of Co-Fe and Ni-Fe electrodes (52% @ RT). However, the 12% B electrodes raised the TMR ratio to 72% at RT when reducing the Al thickness (before oxidation) to 1.2nm (compared to 1.4nm in our standard MTJs). Low temperature measurements showed a TMR value of 114% at 21K and possible explanations for this behavior are discussed.