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TT: Fachverband Tiefe Temperaturen
TT 58: Spincaloric Transport I (jointly with MA)
TT 58.2: Talk
Wednesday, March 18, 2015, 09:45–10:00, H 0110
High tunnel magneto-Seebeck effect — •Alexander Boehnke1, Marvin von der Ehe2, Christian Sterwerf1, Christian Franz3, Michael Czerner3, Karsten Rott1, Andy Thomas1, Christian Heiliger3, Markus Münzenberg2, and Günter Reiss1 — 1CSMD, Physics Department, Bielefeld University, Germany — 2Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, Germany — 31. Physikalisches Institut, Justus-Liebig-Universität Gießen, Germany
Semiconducting materials are known to have large Seebeck coefficients. This is mainly attributed to the gap in their band structure and the asymmetric position of the Fermi-level with respect to this gap. Accordingly, half-metals with a band-gap for only one spin-channel may have very different Seebeck coefficients for the majority and minority charge carriers. The tunnel magneto-Seebeck effect (TMS) is a powerful tool to investigate such spin-dependent Seebeck coefficients because separate spin-channels can be defined in magnetic tunnel junctions (MTJs).
Here, we probe the spin-dependent Seebeck coefficients of half-metallic Heusler compounds in Heusler/MgO/CoFe MTJs. For Co2FeSi we found a TMS ratio of 96%, which is much larger than that of CoFeB/MgO/CoFeB MTJs (4%). Furthermore, we found an increase in the mean Seebeck voltage from 30µV in CoFeB to 3mV in Co2FeSi based MTJs, which agrees with ab initio calculations. We will explain these findings by a Julliere-like model, which also shows the importance of the asymmetric Fermi-level position.