Berlin 2012 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 53: Joint Session Magnetic Shape Memory Alloys II (jointly with DS, MA)

MM 53.14: Vortrag

Donnerstag, 29. März 2012, 18:30–18:45, H 0112

High resolution surface study of modulation in martensites. — •Aleksej Laptev¹, Mikhail Fonin¹, Yuansu Luo², Konrad Samwer², Emmanouel Pagounis³, and Markus Laufenberg³ — ¹Fachbereich Physik, Universität Konstanz, 78457 Konstanz — ²I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen — ³ETO MAGNETIC GmbH, 78333 Stockach, Germany

In our work we address the preparation of high-quality surfaces of Ni-Mn-Ga single crystals with different stoichiometries as well as of epitaxial Ni-Mn-Ga films [1] and the investigation of their surface structure down to the atomic scale by variable temperature scanning tunneling microscopy (VT-STM) in ultra-high vacuum (UHV) conditions. The (001)-oriented sample surface was studied at different temperatures in both austenitic and martensitic phase. The samples reveal on the nanometer scale in the martensitic state a pronounced surface corrugation which was shown to arise from the modulation in martensites [2]. For off-stoichiometric samples seven- (films) and ten-layered (single crystal) modulation periodicities were found. Atomically resolved pictures reveal atomic rows stacked in sequences with varying periods and occasional stacking faults. On the other hand the stoichiometric single crystal with the 5M modulation shows a very regular modulation periodicity and a different shape of the modulation corrugation. This work was supported by the BMBF-Projects MSM-Sens 13N10061 and 13N10062.
Y. Luo et al., New J. Phys. 13, 013042 (2011).
P. Leicht et al., New J. Phys. 13, 033021 (2011).