Open Access
Article Number 04002
Number of page(s) 7
Section Principles, Simulations, Materials: Advanced Materials
Published online 01 September 2009
ESOMAT 2009, 04002 (2009)
DOI: 10.1051/esomat/200904002

The effect of post annealing on structure, microstructure and magnetic prop erties of thin Ni-Mn-Ga films

Anja Backen1, 2, Robert Niemann1, Stefan Kaufmann1, Jörg Buschbeck1, Ludwig Schultz1, 2 and Sebastian Fähler1

1  IFW Dresden, P.O. Box 270116, 01171 Dresden, Germany
2  Dresden University of Technology, Departement of Mechanical Engineering, Institute of Materials Science, 01062 Dresden, Germany

Published online: 1 September 2009

The magnetic shape memory (MSM) alloy Ni-Mn-Ga is an active material where large strains are obtained by magnetically induced reorientation (MIR) of martensitic variants. For the integration in microsystems, epitaxial thin films are in the centre of interest since the highest strains have only been obtained in single crystals. In order to minimize the technological effort, sputter deposition at low deposition temperatures is favoured. However, for obtaining high degree of order and thus a high Curie temperature, an additional post heat treatment at elevated temperatures is necessary. We report on the consequences of the post annealing process on thin epitaxial Ni-Mn-Ga films. In addition to increasing the Curie temperature, the annealed film shows a secondary Ni-rich Ni3 (Mn,Ga) phase. This phase has a well defined interface to the high temperature austenitic phase of Ni-Mn-Ga. Ni3 Ga is formed due to evaporation losses of Mn and Ga. The formation of those precipitates can be avoided by preparing thin Ni-Mn-Ga films directly at elevated temperatures.

© Owned by the authors, published by EDP Sciences 2009