Study On Preparation Technology And Crystallization Behavior And Martensitic Transformation Of Ni-Mn-In Shape Memory Alloy Thin Film

Ni-Mn-In magnetic shape memory alloy thin films have been fabricated by using radiofrequency magnetron sputtering technique. The effect of preparation technology on chemical compositions and surface morphology of Ni-Mn-In thin films has been investigated. The crystallization and martensitic transformation behavior of Ni-Mn-In magnetic shape memory alloy thin films have been systematically studied by means of XRD, DSC. In addition, the mechanism of magnetically driven martensitic transformation has been revealed in the Ni-MnIn based alloy.The experimental results indicate that with increasing sputtering power, the change of Ni, Mn and In content in Ni-Mn-In thin films is not obvious. This demonstrates that the sputtering power has little effect on the content of these elements. Moreover, it is shown that Ni content in Ni-Mn-In thin films increases with increasing the substrate negative bias voltage. Mn content increases with increasing substrate negative bias voltage, while In content decreases linearly with the increase of substrate negative bias voltage. The surface roughness of thin film increases with increasing Ar working pressure and sputtering power.It is found that the film is in the part of the crystalline state when the substrate is not heated. After annealing at 600 ℃ for 1 hour, The width of characteristic diffraction peaks of the film and their intensity increase. There are two endothermic and exothermic peaks in the DSC heating and cooling curves of free constraint Ni-Mn-In alloy film fabricated at 400 ℃. The endothermic peak and exothermic peak at low temperature indicate that thin film undergoesthermal-elastic martensitic transformation during heating and cooling. The endothermic peak and exothermic peak at high temperature are caused by the magnetic transitions of the thin film.In addition, the crystal structure, the band, density of states and magnetic properties of the Ni50Mn25+x In25-x have been calculated by first-principles method based on density functional theory. Furthermore, the unique magnetic properties and magnetostructural transformation of the Ni-Mn-In alloy film have been revealed. The results show that martensite is more stable than parent phase in Ni50Mn37.5In12.5 alloy, which is mainly due to the stronger hybridization of Ni 3dMn 3d in Ni50Mn37.5In12.5 alloy.