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MM: Fachverband Metall- und Materialphysik

MM 38: Topical Session Diffussionless Transformations I

MM 38.1: Topical Talk

Thursday, March 17, 2011, 14:00–14:30, IFW D

Epitaxial films of the magnetic shape memory alloy Ni2MnGa — •Gerhard Jakob, Tobias Eichhorn, Richard Hausmanns, Peter Klaer, Michael Kallmayer, and Hans-Joachim Elmers — Institute of Physics, Johannes Gutenberg-University Mainz

While large magnetically induced strains up to 10% have been observed for bulk single crystals of Ni₂MnGa, these large effects have not been demonstrated for thin films of this compound yet. The preparation of free standing single crystalline films turns out to be a challenging task, but is a necessary precondition for applications on smallest scale.
We report on the preparation and investigation of thin epitaxial films of the NiMnGa-system via dc-magnetron sputtering from an alloy target to heated substrates as Al2O3(11-20), MgO(100) and NaCl(100). The complex crystal structure is studied by temperature dependent x-ray diffraction in 4-circle geometry, whereas magnetic properties are investigated by magnetometry. To avoid blocking effects of the substrate free standing films were prepared by introduction of a buffer layer on MgO(100) that can be etched away selectively.
Using X-ray absorption spectroscopy we determined the element specific magnetic moments and found a remarkable change of the Ni X-ray absorption spectra occurring at the temperature of the phase transition (Tm) which indicates specific changes of the electronic structure. The observed changes are in agreement with theoretical predictions.
This work is part of the DFG priority program SPP 1239.