Regensburg 2004 – scientific programme
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MA: Magnetismus
MA 24: Symposium Magnetic Shape Memory Alloys (zusammen mit M)
MA 24.3: Talk
Thursday, March 11, 2004, 12:15–12:30, H23
A study of ferromagnetic NiMnGa sputtered films including shape memory properties — •Holger Rumpf1, Corneliu Craciunescu2, Manfred Wuttig1,3, and Eckhard Quandt1 — 1Stiftung Caesar, Ludwig-Erhard-Allee 2, 53175 Bonn, D — 2Politehnica University of Timisoara, Romania — 3Department of Materials Science, University of Maryland, College Park, MD, U.S.A.
Off-stoichiometric Ni2MnGa thin films were deposited by DC magnetron sputtering technique. Freestanding thin films as well as Ni50Mn30Ga20/Mo composites were fabricated. Rapid thermal annealing at temperatures equal or higher 500C led to polycrystalline films revealing the reversible martensitic transformation. Transformation temperatures and work output of the transformation were strongly influenced by the temperature of the annealing process as demonstrated by DSC results and cantilever deflection mode measurements. Magnetization experiments disclose a Curie temperature of 103C in accordance with results from NiMnGa single crystals. The shape of the ferromagnetic hysteresis is significantly effected by the annealing temperature. Magnetic field induced strains of freestanding films biases by an external load of several MPa revealed elongations of ca. 0.1 per cent at 200 mT.