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Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 39: Magnetism in Thin Films: Interaction Phenomena and Heterostructures

DS 39.5: Talk

Friday, February 29, 2008, 11:45–12:00, H 2032

Structural characterization and magnetization profile of CoFeB/MgO multilayers for Magnetic Tunnel Junctions — •Miriana Vadalà1, Kirill Zhernenkov1, Max Wolff1, Oleg Petracic1, Kurt Westerholt1, Boris P. Toperverg1, Hartmut Zabel1, Piotr Wisniowski2, and Susana Cardoso21Experimentalphysik/Festkörperphysik, Ruhr-Universität Bochum, Germany — 2INESC, Lisbon, Portugal

We present structural and magnetic results from the characterization of CoFeB/MgO multilayers sputtered at different deposition pressures on Si/SiO2 substrates. From X-ray scans we obtain the layer thicknesses and the interface roughnesses. Magnetic measurements show different results depending on the growth conditions. For all samples the magnetic anisotropy is negligible as intended by the growth of amorphous CoFeB layers. For smooth layers (lower Ar pressure) one finds a step-like hysteresis curve, whereas the curves are strongly rounded for the rougher system (higher Ar pressure). This could hint to a more decoupled vs. a stronger coupled remagnetization behavior, respectively. To shed more light on the behaviour of the alloy at the interface to the MgO layer, we have taken polarized neutron reflectivity data [1]. Similar to the FeCo/Al2O3 system [2] we observe for the multilayer with rough interfaces a loss of a ferromagnetic correlation at remanence, indicating that each CoFeB layer forms an uncorrelated domain structure. Financial support EU-RTN ULTRASMOOTH, SFB 491 and BMBF 03ZA6BC1 are acknowledged.

[1] M. Wolff, et al. Thin Solid Films 515, 5712 (2007)

[2] S. Bedanta, et al , PRB 74, 054426 (2006).

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