Berlin 2008 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

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

DS 39.5: Vortrag

Freitag, 29. Februar 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 Cardoso² — ¹Experimentalphysik/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).