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Berlin 2008 – scientific programme

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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

Tuesday, February 26, 2008, 15:15–18:30, Poster E

Magnetic tunnelling junctions with Co2MnSi, Co2MnSn and Cu2MnAl- Heusler alloy electrodes — •Mohamed Obaida1, 2, Hasan Inam1, Erik Verdijun1, Kurt Westerholt1, and Hartmut Zabel11Institute 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.

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