Regensburg 2010 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 8: Magnetic Shape Memory Alloys
MA 8.8: Vortrag
Montag, 22. März 2010, 17:00–17:15, H22
Microstructure of adaptive martensite in Ni-Mn-Ga — •Sebastian Fähler1,2, Stefan Kaufmann1,2, Robert Niemann1,2, Tom Thersleff1, Oleg Heczko3,1, Bernhard Holzapfel1,2, and Ludwig Schultz1,2 — 1IFW Dresden, PO Box 270116, 01171 Dresden — 2Institute for Solid State Physics, Department of Physics, Dresden University of Technology, 01062 Dresden — 3Institute of Physics, Czech Academy of Science, Na Slovance 2, CZ-182 21 Praha 8
Recently we showed that modulated phases in the Ni-Mn-Ga magnetic shape memory alloy can be interpreted within Khachaturyan's concept of adaptive martensite and described as a nanotwinned microstructure of a basic tetragonal martensite [S. Kaufmann et al. arXiv:0906.5365v1]. The observed coexistence of austenite, 14M and NM martensite in thin films indicated that the transition between 14M and NM proceeds through coarsening of twin boundaries. Here we present a detailed study of the microstructure of an epitaxial film using FIB, AFM and SEM. At the first glance, the microstructure images appear more like modern art than physics. However, it can be shown that this microstructure arises from simple geometrical concepts. A quantitative analysis demonstrates that branching of twin boundaries occurs down to atomic scale and it controls twin width and periodicity over lengthscales more than 3 orders of magnitude.