Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 28: Spin-dependent Transport Phenomena
MA 28.2: Vortrag
Donnerstag, 25. März 2010, 15:30–15:45, H3
Direct measurement of the spin polarization of Co2FeAl — •Oliver Schebaum1, Daniel Ebke1, Andrea Niemeyer1, Günter Reiss1, Jagadeesh S. Moodera2, and Andy Thomas1 — 1Thin Films and Physics of Nanostructures, Bielefeld University, Germany — 2Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
Heusler compounds are of great interest in materials science due to the predicted 100% spin polarization. A high spin polarization of the tunneling current is necessary for a large tunnel magnetoresistance (tmr) ratio. A large tmr ratio is a key requirement for spintronic applications. Thus, Heusler compounds are considered promising candidates as ferromagnetic electrodes in future spintronic devices based on magnetic tunnel junctions (mtjs). Although the room temperature tmr ratio of Heusler based mtjs could be increased in the recent years the enormous effect expected for highly spin polarized electrodes has not been observed.
We directly measured the spin polarization of Co2FeAl in contact with a MgO tunnel barrier by spin polarized tunneling into a superconducting Al-Si electrode. The BCS density of states of the superconductor is spin split in an in-plane magnetic field. Due to this Zeeman splitting a spin polarized tunneling current results in an asymmetry of the conductance vs. voltage measurements.
We found a spin polarization of the tunneling current of P=55%. This value is in good agreement with the spin polarization obtained from our tmr measurements and results published by other groups.