Title

Characterization of Mechanical and Magnetic Properties of Ni-Mn-Ga Shape Memory Thin Films Deposited onto Silicon and Alumina Substrates

Publication Date

11-2008

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Mechanical Engineering

Department

Mechanical and Biomechanical Engineering

Major Advisor

Peter Müllner

Abstract

The mechanical and magnetic properties of off-stoichiometric Ni2MnGa shape memory thin films deposited onto silicon and alumina substrates at different thicknesses are examined. Two sets of films were deposited onto silicon(100) substrates and one set of films were deposited onto polycrystalline alumina. The films deposited onto silicon had a composition of Ni49.5Mn28.0Ga22.5 and Ni51.4Mn28.3Ga20.3. The films deposited onto the alumina substrates had a composition of Ni51.4Mn28.3Ga20.3. Substrate curvature measurements were performed to characterize the martensitic phase transformation temperature, the in-plane film stress change during the phase transformation, and the biaxial modulus of each film. Vibrating sample magnetometry was performed to characterize the Curie temperature and the magnetic anisotropy of each film. The crystallographic texture was characterized for a set of films deposited onto silicon using x-ray diffraction techniques. The martensitic transformation temperature increased with increasing film thickness on the Ni51.4Mn28.3Ga20.3 and decreased with increasing film thickness for the Ni49.5Mn28.0Ga22.5 films. The magnitude of the in-plane stress change during the phase transformation showed an increasing trend with increasing film thickness for the Ni51.4Mn28.3Ga20.3 films and a decreasing trend for the Ni49.5Mn28.0Ga22.5 films. For each set of films, there was a thickness dependence of the biaxial modulus for the films. The Curie temperature was not effected by film thickness. For the films deposited onto alumina substrates, a thickness dependence of the magnetic anisotropy was observed. The mechanical and magnetic properties of the Ni-Mn-Ga films showed both a compositional and thickness dependence.

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