A fabrication technology for epitaxial Ni-Mn-Ga microactuators
University of Karlsruhe, IMT, Hermann-von-Helmholtz Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
2 Forschungszentrum Karlsruhe, IMT, Postfach 3640, 76021 Karlsruhe, Germany
3 IFW Dresden, Institute for Metallic Materials, PO Box 270116, 01171 Dresden, Germany
This paper reports on the fabrication and characterization of epitaxial Ni-Mn-Ga microactuators. Ni-Mn-Ga films are grown on heated single-crystalline MgO substrates by DC magnetron sputtering. X-ray diffraction measurements demonstrate epitaxial growth of the films. At room temperature, the crystal structure is identified to be non-modulated (NM) tetragonal martensite. Electrical resistance measurements confirm that the films display the martensitic phase transformation well above the Curie temperature TC of 325 K. Orientation-dependent magnetization measurements are performed to determine magnetic film properties. Micromachining of the Ni-Mn-Ga films is performed on an alumina substrate covered by a temporary adhesive layer. A transfer bonding process is developed to finally integrate the micromachined Ni-Mn-Ga structures to a target substrate in order to obtain NiMnGa microactuators having freely movable microparts. Temperature-displacement characteristics demonstrate the actuation performance of epitaxial NiMnGa microactuators for the first time.
© EDP Sciences, Springer-Verlag, 2008