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MA: Fachverband Magnetismus

MA 25: Magnetic Shape Memory Alloys II (jointly with MM)

MA 25.4: Talk

Tuesday, March 15, 2011, 14:15–14:30, HSZ 103

Atomically resolved surface structure of (100)-oriented thin epitaxial Ni-Mn-Ga films. — •Aleksej Laptev¹, Philipp Leicht¹, Mikhail Fonin¹, Yuansu Luo², and Konrad Samwer² — ¹Fachbereich Physik, Universität Konstanz, 78457 Konstanz — ²I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen

Epitaxial off-stoichiometric Ni-Mn-Ga films were deposited on MgO(100) substrates by dc magnetron sputtering. After appropriate cleaning steps in ultra high vacuum conditions the (100)-oriented film surface was studied at room temperature by means of scanning tunneling microscopy (STM). In the austenitic state well-ordered surface exhibiting predominantly Mn-Ga termination was observed. After a transformation of the sample to the martensitic state upon a high temperature annealing step the martensitic surface was investigated at room temperature. On a larger scale STM images show a zig-zag shaped surface topography due to the formation of twin boundaries [1]. A second corrugation feature is found on every second side of twin lamellae originating from the modulated nature of martensites. The irregularly-spaced corrugation lines and the observed atomic structure on both sides of the twin variants support the stacking approach of the modulated superstructure proposed within the model of adaptive martensites [2]. This work was supported by BMBF-Projects MSM-Sens 13N10061 and 13N10062.

[1] J. Buschbeck et al., Acta Mater. 57, 2516-2526 (2009)

[2] S. Kaufmann et al., Phys. Rev. Lett. 104, 145702 (2010)