Regensburg 2007 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 12: Spindependent Transport I

MA 12.2: Vortrag

Dienstag, 27. März 2007, 10:30–10:45, H22

Transport properties of magnetic tunnel junctions with the quaternary Heusler alloy Co₂Mn_0.5Fe_0.5Si — •Daniel Ebke¹, Jan Schmalhorst¹, Andreas Hütten¹, Günter Reiss¹, Benjamin Balke², and Claudia Felser² — ¹Thin Films and Nanostructures, Department of Physics, Bielefeld University, 33501 Bielefeld, Germany — ²Institute for Inorganic and Analytical Chemistry, Johannes Gutenberg University, 55099 Mainz, Germany

Due to the half metallic character predicted by band structure calculations and because of the high Curie temperature the Heusler alloys Co₂MnSi and Co₂FeSi are promissing canditates for spintronic applications. Both alloys, as well as a multilayered Heusler electrode, have been integrated sucessfully into magnetic tunnel junctions (MTJs) in the past. In case of the multilayered electrode TMR ratios of more than 110% can be observed at 20K and about 40% at RT, respectively. Recently, Balke et al have shown band structure calculations for the quaternary Heusler alloy Co₂Mn_1−xFe_xSi and found a shift of the Fermy energy from the top of the valence band to the bottom of the conduction band with a increase of the Fe concentration. To enhance the TMR ratio for Heusler alloys at room temperature as well, we have integrated the Heusler alloy Co₂Mn_0.5Fe_0.5Si into MTJs as the bottom electrode. We will present the resulting TMR effect amplitudes in dependence of preparation conditions and the thickness of the AlO_x barriere. The temperature dependence of the TMR ratio will be discussed in combination with magnetic and XRD measurements.