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MA: Fachverband Magnetismus

MA 12: Spindependent Transport I

MA 12.3: Vortrag

Dienstag, 27. März 2007, 10:45–11:00, H22

Temperature dependence of resistance and TMR in MgO based tunnel junctions — •Volker Drewello, Andy Thomas, and Günter Reiss — Bielefeld University, Universitätsstraße 25, 33615 Bielefeld

In magnetic tunnel junctions the widely used Alumina barriers are more and more replaced with MgO, which shows much higher TMR rates. While Alumina based junctions show quite big temperature dependence of the conductance in parallel magnetic state, it is commonly observed that this tendency is much smaller in MgO junctions.

We have prepared MgO based tunnel junctions with CoFeB electrodes. The junctions show TMR of over 140% at room temperature, which increases by a factor of 1.4 when temperature is decreased to 12 K. The parallel resistance however only changes by 8% so that the chance of the TMR is mainly the change of the anti parallel resistance. This behavior is also observed in MgO junctions with higher TMR and different electrode materials [1, 2].

Different existing models for the TMR temperature dependence of these junctions are discussed. We will see that that these can describe the MgO junctions temperature dependence but the physical meaning of the parameters used remains unclear. Therefore, we will present a modified model with convincing results.

[1] S.S.P. Parkin et. al., Nat. Mat. 3, 862 (2004)

[2] T. Ishikawa et. al., Appl. Phys. Lett. 89, 192505 (2006)