Regensburg 2002 – wissenschaftliches Programm

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DS: Dünne Schichten

DS 27: Postersitzung

DS 27.43: Poster

Dienstag, 12. März 2002, 15:30–17:30, Poster Physik B

Superconductivity of MgB₂ thin films prepared by co-evaporation and magnetism of MgB₂/Fe multilayers studied by Mössbauer spectroscopy — •B. Sahoo, V. Kuncser, S. Kirsch und W. Keune — Angewandte Physik, Gerhard-Mercator-Universität Duisburg, 47048 Duisburg

The recently discovered MgB₂ superconductor presents both applicative and fundamental interest due to its high transition temperature (T_C=39K) among the metallic superconductors. Moreover it might be a good material to study the proximity effect or magnetism at the interface of superconductor/ferromagnet multilayers. MgB₂ thin films and MgB₂/Fe multilayers with different thickness have been prepared by vacuum deposition of the elements. The hexagonal structure of MgB₂ was characterized by X-ray diffraction (XRD), demonstrating textured growth with preferred c-axis orientation. Superconducting transition temperatures of 18K and 22K have been measured, respectively, before and after annealing a MgB₂ film of 160 nm thickness. Atomic force microscope (AFM) image shows a three-dimensional type of growth with very rough surface. Magnetic phenomena related to microstructural aspects in (MgB₂/Fe)_n multilayers were studied by conversion electron Mössbauer spectroscopy (CEMS) at various temperatures. Metallic iron and iron-boron phases as well as a high amount of iron atoms diffused into the MgB₂ layer were evidenced near the interface. The magnetic patterns in the low temperature Mössbauer spectra transform in central paramagnetic patterns at room temperature proving the superparamagnetic behaviour of the Fe based particles.