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arXiv · 1311.5428

Mesoscopic twin boundaries in epitaxial Ni-Mn-Ga films

Anja Backen·Sandra Kauffmann-Weiss·Christian Behler·Anett Diestel·Robert Niemann·Alexander Kauffmann·Jens Freudenberger·Ludwig Schultz·Sebastian Fähler
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Abstract

Twin boundaries play an essential role in the use of magnetic shape memory alloy Ni-Mn-Ga as active material. Only if twin boundaries can be moved by an external magnetic field, high strain values of up to 10 % can be obtained. Therefore, understanding the observed twin microstructure of thin films is crucial for future application. We exemplarily present two different microstructural pattern, type X and type Y microstructure, using the example of two Ni-Mn-Ga films with similar film thickness and composition. The analysis of microstructure and structure of the thin films shows that both, type X and type Y pattern, are formed by mesoscopic 14M twin boundaries. The mesoscopic 14M twin boundaries are either tilted from the substrate surface in case of type X pattern or they are perpendicular to the surface for type Y pattern. Based on a recently proposed scenario for the nucleation of martensite in austenite, we can trace back the difference in twin boundary orientation to differently oriented martensitic nuclei.

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Anja Backen, Sandra Kauffmann-Weiss, Christian Behler, Anett Diestel, Robert Niemann, Alexander Kauffmann, Jens Freudenberger, Ludwig Schultz, Sebastian Fähler. 2013-11-21. Mesoscopic twin boundaries in epitaxial Ni-Mn-Ga films. https://arxiv.org/abs/1311.5428

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