Berlin 2008 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 18: Poster I : Bio Magn. (1-2); Mag.Imgaging (3-9); Magn. Semiconductors (10-16); Half Metals & Oxides (17-20); Coupl.Phenomena (21-27); Magn. Mat. (28-41); Micro & Nanostr. Magn. Materials (42-61); Micro Magn. (62-64); Surface Magnetism (65-70); Transport Phenomena (71-85)

MA 18.81: Poster

Dienstag, 26. Februar 2008, 15:15–18:30, Poster E

Magnetic tunnelling junctions with Co₂MnSi, Co₂MnSn and Cu₂MnAl- Heusler alloy electrodes — •Mohamed Obaida^{1, 2}, Hasan Inam¹, Erik Verdijun¹, Kurt Westerholt¹, and Hartmut Zabel¹ — ¹Institute für Experimentalphysik IV Ruhr-Universität Bochum, 44780 Bochum, Germany — ²National Research Center, Cairo, Egypt

We fabricated magnetic tunnelling junctions (MTJs) using Heusler half metallics Co₂MnSi, and Co₂MnSn as base electrodes and Al₂O₃ or MgO as barrier material. As the counter electrode we used Co. The Heusler layers were deposited by UHV magnetron sputtering on oxidized SiO₂ substrates, the barriers were prepared by plasma oxidation of Al or direct sputtering of MgO, respectively. For Co₂MnSi we get a tunnelling magnetoresistance (TMR) of 27% at low temperatures, for the case of the Co₂MnSn electrode the maximum value we observed was 12%, however for this junction we could not avoid Neel coupling between the ferromagnetic electrodes so that the antiferromagnetic orientation was not well defined. We have also tried to grow MgO barriers on the Heusler alloy half metallics, however it turned out to be very difficult to get pinhole free barriers on this electrodes by direct sputtering of MgO. We have also started to grow MgO barriers on the Heusler phase Cu₂MnAl, which actually is not half metallic but is perfectly lattice matched to MgO and could serve as a reference material for Heusler MTJs. On this material we get high quality, pinhole free barriers, but the TMR we observed until now is still small.