Regensburg 2007 – scientific programme

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DS: Fachverband Dünne Schichten

DS 15: Poster Session

DS 15.24: Poster

Tuesday, March 27, 2007, 15:00–17:00, Poster B

Structural Properties of CoFeB/MgO Magnetic Tunnel Junction Multilayers — •Miriana Vadala, Alexei Nefedov, Gregor Nowak, Arndt Remhof, Kurt Westerholt, and Hartmut Zabel — Experimentalphysik/Festkörperphysik, Ruhr-Universität Bochum, Germany

The focus of the spintronics community is presently on CoFeB/MgO based Magnetic Tunnel Junctions (MTJs). Tunnel Magneto Resistance values above 200 % at room temperature with a crystalline MgO barrier have already been reported. Depending on the boron content, annealing at low temperatures, typically in the range from 270^∘C to 360^∘C, leads to a re- crystallisation of CoFeB. We present results from the characterization of different series of CoFeB/MgO multilayers grown on a Si/SiO₂ substrate, synthesized by ion beam deposition. Key parameters for MTJs are the single-layer thickness, the growth process of the oxide barriers, and the annealing temperatures. They rule the degree of re-crystallization of the CoFeB/MgO together with the interface roughness. Three different growth procedures for the MgO spacer layers have been tested. Polarized neutron reflectivity data confirm that reactive deposition provides the proper stoichiometry for MgO. From X-ray specular and transverse diffuse reflectivities we obtain the structural parameters, namely the layer thickness and the interface roughness. Although the layer thickness does not vary with the annealing procedures, the roughness slightly changes before and after annealing. Financial support provided through the EU-RTN *ULTRASMOOTH*, support by SFB 491 and by BMBF 03ZA6BC1 is acknowledged.