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End date: 2019 × End date: 2016 × Start date: 2010 × Version: publishedVersion × Subject: Nickel ×

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Now showing 1 - 3 of 3
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    Thickness dependent exchange bias in martensitic epitaxial Ni-Mn-Sn thin films
    (New York : American Institute of Physics, 2013) Behler, Anna; Teichert, Niclas; Dutta, Biswanath; Waske, Anja; Hickel, Tilmann; Auge, Alexander; Hütten, Andreas; Eckert, Jürgen
    A thickness dependent exchange bias in the low temperature martensitic state of epitaxial Ni-Mn-Sn thin films is found. The effect can be retained down to very small thicknesses. For a Ni50Mn32Sn18 thin film, which does not undergo a martensitic transformation, no exchange bias is observed. Our results suggest that a significant interplay between ferromagnetic and antiferromagnetic regions, which is the origin for exchange bias, is only present in the martensite. The finding is supported by ab initio calculations showing that the antiferromagnetic order is stabilized in the phase.
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    Structural evolution in Ti-Cu-Ni metallic glasses during heating
    (New York : American Institute of Physics, 2015) Gargarella, P.; Pauly, S.; Stoica, M.; Vaughan, G.; Afonso, C.R.M.; Kühn, U.; Eckert, J.
    The structural evolution of Ti50Cu43Ni7 and Ti55Cu35Ni10 metallic glasses during heating was investigated by in-situ synchrotron X-ray diffraction. The width of the most intense diffraction maximum of the glassy phase decreases slightly during relaxation below the glass transition temperature. Significant structural changes only occur above the glass transition manifesting in a change in the respective peak positions. At even higher temperatures, nanocrystals of the shape memory B2-Ti(Cu,Ni) phase precipitate, and their small size hampers the occurrence of a martensitic transformation.
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    Transformation of epitaxial NiMnGa/InGaAs nanomembranes grown on GaAs substrates into freestanding microtubes
    (Cambridge : Royal Society of Chemistry, 2016) Müller, C.; Neckel, I.; Monecke, M.; Dzhagan, V.; Salvan, G.; Schulze, S.; Baunack, S.; Gemming, T.; Oswald, S.; Engemaiere, V.; Mosca, D.H.
    We report the fabrication of Ni2.7Mn0.9Ga0.4/InGaAs bilayers on GaAs (001)/InGaAs substrates by molecular beam epitaxy. To form freestanding microtubes the bilayers have been released from the substrate by strain engineering. Microtubes with up to three windings have been successfully realized by tailoring the size and strain of the bilayer. The structure and magnetic properties of both, the initial films and the rolled-up microtubes, are investigated by electron microscopy, X-ray techniques and magnetization measurements. A tetragonal lattice with c/a = 2.03 (film) and c/a = 2.01 (tube) is identified for the Ni2.7Mn0.9Ga0.4 alloy. Furthermore, a significant influence of the cylindrical geometry and strain relaxation induced by roll-up on the magnetic properties of the tube is found.