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Acta Materialia, Volume 86, 2015, Pages 279–285.
Teichert1, A. Auge1, E. Yüzüak2,3, I. Dincer2, Y. Elerman2, B. Krumme4, H. Wende4, O. Yildirim5,6, K. Potzger5, A. Hütten1.
[expand title=”Show Affiliations”]- Center for Spinelectronic Materials and Devices, Physics Department, Bielefeld University, 33615 Bielefeld, Germany
- Department of Engineering Physics, Faculty of Engineering, Ankara University, 06100 Besevler, Ankara, Turkey
- Department of Nanotechnology Engineering, Faculty of Engineering, Recep Tayyip Erdogan University, 53100 Rize, Turkey
- Faculty of Physics and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, 47048 Duisburg, Germany
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, PO Box 510119, 01314 Dresden, Germany
- Institute for Physics of Solids, Technical University Dresden, Zellescher Weg 16, 01069 Dresden, Germany
Abstract
Two series of epitaxial Ni–Mn–Sn thin films of different thickness are investigated for the thickness and composition dependence of the martensitic transformation. Thin films ranging in thickness from 20 to 200 nm (series A) and 10 to 100 nm (series B) were prepared by magnetron co-sputtering and deposited on heated MgO(0 0 1) substrates. The structural characterization was done by temperature-dependent X-ray diffraction measurements. Magnetization and resistivity measurements were performed to investigate the transformation characteristics. We find a strong influence of the film thickness on the relative amount of material undergoing the martensitic transformation, the temperature range of the transformation, and the transformation temperatures. The main contribution originates from the rigid substrate which delays the transformation of the Ni–Mn–Sn near the interface and even leads to a layer of residual austenite at low temperatures. Another issue are size effects which presumably broaden the martensitic transformation and decrease the transformation temperatures. By variation of the thin film composition we find changes of the substrate influence due to a different mismatch between the lattice of MgO and austenite. A better phase compatibility between martensite and austenite, denoted by λ2, not only results in a smaller hysteresis but is also beneficial for the transformation of material close to the substrate.
