Martensitic transformation of NiMnGa shape memory alloys thin films studied by flash DSC

Abstract

The martensitic transformation of a magnetic shape memory alloy of composition Ni54Mn24Ga22 has been studied by Flash DSC at 10,000 K/s heating rate. The alloy was deposited directly onto the Flash DSC chip by magnetron sputtering through a metallic mask. The chip was heated at 500 °C during the deposition in order to obtain the correct structure of the films. Adherence of the films to the chip was possible only by depositing a thin Cr buffer layer. The transformation can be detected without problem and the associated enthalpy determined. The transformation temperatures are similar to the values obtained in a witness film. The enthalpy, however, is lower than the corresponding to the bulk alloy, but no reference film of the same characteristics is available for comparison.