Regensburg 2013 – scientific programme

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MA: Fachverband Magnetismus

MA 11: ThyssenKrupp Electrical Steel Dissertationspreis 2013 der AG Magnetismus

MA 11.1: Talk

Monday, March 11, 2013, 12:15–12:40, H3

Direct measurement of the spin polarization by tunneling spectroscopy with superconducting electrodes — •Oliver Schebaum — Thin Films and Physics of Nanostructures, Physics Department, Bielefeld University, Germany

Spinelectronics utilize the spin degree of freedom of electrons, which is neglected by conventional electronics. One promising spinelectronic device is the magnetic tunnel junction (MTJ). The spin polarization of the tunneling current in an MTJ can be altered by the magnetic electrodes as well as the incorporated tunnel barrier material. Tunnel junctions with a unified layer stack were prepared for three different barriers. In these systems, the tunnel magnetoresistance (TMR)ratios at optimum annealing temperatures were found to be 65% for Al2O3, 173% for MgO, and 78% for MgO-Al2O3 composite tunnel barriers. The similar TMR ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier [1]. Furthermore, we prepared tunnel junctions with one ferromagnetic and one superconducting Al-Si electrode. Pure cobalt electrodes were compared with a Co-Fe-B alloy and the Heusler compound Co2FeAl. The polarization of the tunneling electrons was determined using the Maki-Fulde-model and is discussed along with the spin-orbit scattering and the total pair-breaking parameters. The junctions were postannealed at different temperatures to investigate the symmetry filtering mechanism responsible for the giant TMR ratios in Co-Fe-B/MgO/Co-Fe-B junctions.[2,3]

[1] O. Schebaum, V. Drewello, A. Auge, G. Reiss, M. Münzenberg,H. Schuhmann, M. Seibt and A. Thomas, J. Magn. Magn. Mat. 323 (2011) 1525-1528

[2] O. Schebaum, D. Ebke, A. Niemeyer, G. Reiss, J.S. Moodera and A. Thomas, J. Appl. Phys. 107 (2010) 09C717

[3] O. Schebaum, S. Fabretti, J.S. Moodera and A. Thomas, New J. Phys. 14 (2012) 033023