Ni-Mn-Ga Film Analysis

the film. The surface morphology of the films was observed using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The magnetic properties of the films were analyzed using magnetic force microscopy (MFM).

RESULTS AND DISCUSSIONS
The room temperature XRD pattern for the annealed film with the thickness of 135 nm and 260 nm showed the coexistence of both austenite and martensite phase. While increasing the film thickness to 595 nm, L21 cubic structure is observed. Further increase in the film thickness ~1020 nm, the Ni-rich formation occurred which leads to L12 phase structure (non-magnetic) and which was reported in earlier work.7
Fig. 1 shows the 3D configuration of Ni-Mn-Ga thin films sputtered on Si (100) substrate at different thicknesses. The topography images of the films are composed in equiaxied grain and irregular spherical shaped particles are

In general, while increasing the thickness of the film the morphology has been changed. In Fig 1a, NMG1 having the thickness of 135 nm consists of randomly distributed grains about 20 nm. For NMG2 and NMG3, the grains tend to agglomerate and try to enlarge the grain size. With further increase in the film thickness the morphology changes again, which is shown in the Fig 1d. In polycrystalline film, the structural changes occur due to the surface diffusion and grain boundary migration during the coalescence of two differently oriented nuclei. In 3D growth mode, the particles incident on the substrate surface form clusters which start to grow, as a result the atoms are formed as an island. At the initial stage, many nucleation centres are present on the substrate surface. Hence, at lower thickness smaller crystallites are present. In addition, the deposition time is very short for thinner film, so the smaller crystallites cannot grow into larger ones. But the film grown