Annealing Effect On The Magnetic Induced Austenite Transformation In Polycrystalline Freestanding Ni-Co-Mn-In Films Produced By Co-Sputtering

Ni-Co-Mn-In freestanding films, with a magneto-structural transformation at room temperature were successfully produced by co-sputtering and post-annealing methods leading to film composition mastering. For a post-annealing temperature of 700 degrees C, the phase transformation occurs slightly above room temperature, with a twisted martensitic microstructure phase observed at 300K by Field Emission Scanning Electron Microscopy. Magnetization measurements on a poly-crystalline film showed a phase transformation from a weakly magnetic martensite to a magnetic austenite phase. Moreover, an inverse magnetocaloric effect with an entropy variation of 4 J/kg K under 5 T was also measured. A simple magneto-actuation experiment based on the magnetic induced austenite transformation was also successfully completed. The possibility to insert such films in microsystems is clearly demonstrated in this work. (C) 2015 AIP Publishing LLC.