Dresden 2009 – wissenschaftliches Programm
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MA: Fachverband Magnetismus
MA 21: Magnetic Shape Memory Alloys I
MA 21.1: Vortrag
Mittwoch, 25. März 2009, 10:15–10:30, HSZ 103
Straining of Fe70Pd30 Films by Coherent Epitaxial Growth — •Jörg Buschbeck1, Ingo Opahle1,2, Gerhard Jakob3, Ludwig Schultz1, and Sebastian Fähler1 — 1IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany — 2Institute for Theoretical Physics, Johann Wolfgang Goethe University, Frankfurt am Main, Germany — 3Institut für Physik, Johannes Gutenberg-Universität Mainz, D-55128 Mainz, Germany
Martensitic transformations in the Fe70Pd30 magnetic shape memory alloy follow the Bain path, describing the conversion from fcc to bcc structure by a tetragonal distortion. According to density functional calculations, a flat energy landscape is expected along the Bain path. Since changes in tetragonal distortion only cost little energy, this allows for the stabilization of intermartensitic phases in strained Fe70Pd30 films. Straining is realized by pseudomorphic epitaxial growth of Fe70Pd30 films using magnetron-sputtering at room temperature on different epitaxial buffer layer prepared on MgO(100) substrates. Pseudomorphic film growth of 50 nm thick disordered Fe70Pd30 films is observed. In agreement, XRD measurements show a tetragonal distortion in the films which is determined by the lattice parameter of the buffer layer. The tetragonal distortion reaches exceptionally high values of up to 27.5%, covering most of the Bain path from fcc to bcc phase, reflecting the structural instability of Fe70Pd30 as predicted by theory. The stabilization by an epitaxial interface allows for the thorough investigation of the physical properties of intermediate phases inaccessible in bulk materials.