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 53.10: Vortrag
Donnerstag, 29. März 2012, 17:30–17:45, H 0112
Correlation Between Microstructure and Magnetic Properties in Epitaxial Ni-Mn-Ga Thin Films — •Gesa Welker1, Aleksej Laptev1, Mikhail Fonin1, Yuansu Luo2, and Konrad Samwer2 — 1Fachbereich Physik, Universität Konstanz, 78457 Konstanz — 2I. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen
Ni-Mn-Ga and related alloys exhibit a magnetic shape memory effect and have been subject to research due to their large magnetic field induced strain of up to 10% [1]. So far, only few investigation of their magnetic domain structure has been done on thin films [2].
Here we investigate the morphology and magnetic domain configurations in epitaxial Ni-Mn-Ga thin films grown on MgO(001) substrates by dc-magnetron sputtering [3] as well as in free-standing microstructures released from the rigid substrate by etching. We investigated Ni-Mn-Ga films of different compositions and thicknesses at varying temperatures by means of atomic force microscopy (AFM) and magnetic force microscopy (MFM) in remanence. In the martensitic state we found large domains with out-of-plane magnetization. The domain walls are oriented perpendicular to the martensitic twin boundaries direction. On a smaller scale, the magnetic domain structure is governed by the orientation of the easy axis of the martensitic variants.
Our results could be helpful for the construction of microscale actuators or sensors based on Ni-Mn-Ga thin films.[1] K. Ulakko et al.,Scripta Mater. 36, 1133-1138 (1997)[2] Q. Pan et al., J. Appl. Phys. 91, 7812-7814 (2002)[3] Y. Luo et al., J. Phys. 13, 013042 (2011)