Berlin 2012 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 48: Joint Session Magnetic Shape Memory Alloys I (jointly with DS, MA)
MM 48.1: Talk
Thursday, March 29, 2012, 10:15–10:30, H 0106
Different types of twin boundaries in 14M modulated Ni-Mn-Ga — •Christian Behler1,2, Bernd Rellinghaus1, Anja Backen1, Sandra Kauffmann-Weiss1, Ludwig Schultz1,2, and Sebastian Fähler1,2 — 1IFW Dresden, Institute for Metallic Materials, P.O. Box 270116, 01171 Dresden, Germany — 2Dresden University of Technology, Institute for Solid State Physics, Department of Physics, 01062 Dresden, Germany
Recent studies [L. Straka et al. Acta Mat. 59 (2011) 7450-7463] have found that various types of twin boundaries, such as type I, type II and modulation twins, with different mobilities can exist in the magnetic shape memory alloy Ni-Mn-Ga. In a 1.5 µm thin epitaxial Ni-Mn-Ga film we observe two types of twin boundaries. This film was investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) imaging and selected area diffraction (SAED) to clarify the type of the observed boundaries. From the orientations of neighboring variants, determined by SAED, conclusions can be drawn about the type of the interfaces. These analyzed interfaces can be attributed to type I twin boundaries as well as modulation twins. The 14M modulation is generated by nanotwins, which were observed by High Resolution TEM. However, this modulation is not perfect due to the existence of stacking faults.