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MM: Fachverband Metall- und Materialphysik
MM 38: Topical Session Diffussionless Transformations I
MM 38.3: Vortrag
Donnerstag, 17. März 2011, 14:45–15:00, IFW D
Correlating twinning periodicity and film thickness of epitaxial Ni-Mn-Ga films — •Anett Diestel1,2, Anja Backen1,2, Ludwig Schultz1,2, and Sebastian Fähler1 — 1IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, 01171 Dresden, Germany — 2Dresden University of Technology, Department of Mechanical Engineering, Institute of Materials Science, 01062 Dresden, Germany
In order to probe the theoretical geometrical theory by Kiselev et al. [1] about the periodicity of stripe domains in magnetic shape memory alloys, we have analysed the finely twinned microstructure of 14M martensite in epitaxial Ni-Mn-Ga films. Epitaxial Ni-Mn-Ga films with different thicknesses ranging from 30 nm to 2 µm have been deposited by sputter deposition on single crystalline MgO(100) substrates with a chromium buffer layer. The characteristic microstructure of 14M martensite was quantified by atomic force microscopy. The periodic height profiles of the mesoscopic twin boundary formation were analysed according to the geometrical model of a twinned surface by Buschbeck et al. [2]. We observed an increasing twin boundary periodicity with the square root of the film thickness. We did not observe the increase of variant size below a critical thickness predicted by Kiselev et al. We attribute this to the finite number of unit cells involved, an aspect not considered in continuum theory. This work was funded by DFG through SPP 1239. [1] N.S. Kiselev et al. Eur. Phys. J. Special Topics 158 (2008) 119 [2] J. Buschbeck et al. Acta Mater. 57 (2009) 2516