Study On Ferromagnetic Shape Memory Alloy Ni-Mn-Ga Films

The properties of Ni-Mn-Ga films prepared by ECR D.C. magnetron sputtering were preliminary investigated in this paper. The purpose of the research was to probe in this new type of FSMA film.Composition of films was the most important thing in depositing Ni-Mn-Ga films. By comparing the composition of films in different parameters, the optimal one to prepare the film was as follows: 22.5w sputtering power, 60mm between target and substrate, 0.1 Pa argon pressure. At the same time, the influence of different parameters on composition of films was studied.The surface characterization of films was studied through SEM. Grains of different size in micron order were observed. They were gathered by sputtering grains and the presentation of uneven state was determined by the size of them and the time they reached substrate.The morphology of films was studied by AFM. The films were typical nucleation growth and the development of them was described. By comparison of morphology pictures with different substrates, the roughness of films were known greatly affected by substrates.The results of X-ray diffraction indicated that the film of as-deposited state was crystalline and mostly orientated to (022). The average crystalline size perpendicular to (022) lattice face was about 8.503nm while its lattice deformation rate was about 1.36%.Compared with films before heat treatment, the surface of films heat-treated was looked more uniform and more compact. And because the change of film volume with temperature was so different with that of substrate's, the film deposited on NaCl subtract cracked ;while it is similar to that of Cu wafer's, the film deposited on Cu substrate did not break up.The strain of Ni-Mn-Ga film induced by magnetic field was tested. Negative 85ppm was got when applying magnetic field about 13koe parallel to film surface. It was contrasted with that of blocks and the curve of strain was analyzed.The standard indentation test was done to Ni-Mn-Ga film with thickness about 400nm. Elastic modulus of the film was calculated as 3.79GPa while hardness was 252.92MPa.