Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 108: Spin-Dependent Transport Phenomena II (organized by MA)
TT 108.7: Talk
Thursday, March 19, 2015, 16:45–17:00, H 0112
Sign change in tunnel magnetoresistance of Fe3O4/MgO/CoFeB magnetic tunnel junctions depending on annealing temperature and interface treatment — Luca Marnitz1, Karsten Rott1, Stefan Niehörster1, Christoph Klewe1, Daniel Meier1, Savio Fabretti1, Matthäus Witziok2, Andreas Krampf2, Olga Schuckmann2, Tobias Schemme2, Karsten Kuepper2, Joachim Wollschläger2, Andy Thomas1, Günter Reiss1, and •Timo Kuschel1 — 1CSMD, Physics Department, Bielefeld University, Germany — 2Physics Department, Osnabrück University, Germany
Magnetite (Fe3O4) is a promising candidate for magnetic tunnel junctions (MTJs) since it shows a high spin polarization at the Fermi level as well as a high Curie temperature of 585∘C. However, MTJs with magnetite electrodes have not shown a large tunnel magnetoresistance (TMR) so far. It is reported in literature for magnetite on MgO that Mg2+ ions diffuses into the magnetite at growth temperatures above 250∘C, replacing parts of the Fe2+ ions. In typical magnetite MTJs MgO is used both as substrate as well as barrier material.
In this study, a sign change in the TMR of Fe3O4/MgO/CoFeB MTJs is observed after annealing at temperatures between 200∘C and 280∘C which can be explained by Mg interdiffusion from the MgO barrier into the magnetite. Additionally, different treatments of the magnetite interface during the preparation of the MTJs have been studied regarding their effect on the performance of the MTJs. A maximum TMR of up to -12% was observed despite exposing the magnetite surface to atmospheric conditions prior to the deposition of the MgO barrier.