Thickness dependent phase transformation of magnetron-sputtered Ni–Mn–Sn ferromagnetic shape memory alloy thin films

Phase transformation in Ni–Mn–Sn ferromagnetic shape memory alloy thin films induced by dense ionization

“…1. XRD analysis reveals the formation of martensitic phase in pristine film, and the planes corresponding to martensitic structure are marked by their Miller indices [21][22][23][24]. The lattice constants a, b, and c are estimated to be about 0.4, 0.5 and 2.9 nm, which agrees with the previously reported values of lattice constants for bulk [25].…”

“…At a fluence of 1 × 10 12 ions/cm 2 , grains are more diffused, and it is difficult to observe the boundary of the grains. In the FESEM micrograph of the film irradiated at 3 × 10 12 ions/cm 2 , pyramidical shaped grains are observed, confirming the phase transformation from martensite to austenite phase [21][22][23][24]. At a fluence of 6 × 10 12 ions/cm 2 , pyramidical grains with well defined boundaries are clearly observed.…”

Multiple effects of Ni-rich precipitates in Ni–Ti–Al thin films

“…It can be seen clearly that resistivity of the films deposited at 450 and 500 1C decreases firstly and then increases obviously during the cooling stage. The change trend of resistivity with testing temperature is similar to martensitic transformation of L2 1 phase in Ni 50 Mn 36 Sn 14 Heusler alloys [31]. The Heusler alloys, including Ni 2 MnSn [31], Ni 2 FeGa [32] and Ni 2 MnGa [33], have been proved to be unstable during cooling and the Heusler phases can be transformed into the relevant low-temperature martensitic phases.…”

“…The change trend of resistivity with testing temperature is similar to martensitic transformation of L2 1 phase in Ni 50 Mn 36 Sn 14 Heusler alloys [31]. The Heusler alloys, including Ni 2 MnSn [31], Ni 2 FeGa [32] and Ni 2 MnGa [33], have been proved to be unstable during cooling and the Heusler phases can be transformed into the relevant low-temperature martensitic phases. Inflection point of the resistivity in the film deposited at 450 1C situates À 37.5 1C, and it is increased to À33.7 1C with increasing the T d to 500 1C.…”

Martensitic phase transformations and magnetocaloric effect in Al co-sputtered Ni–Mn–Sb alloy thin films

“…Since the martensite phase has higher resistance as compared with the austenite phase, the value of overall resistance decreases with increasing temperature, showing semiconductor behaviour around the transformation temperature [39]. The sharp decrease of electrical resistance during martensitic transformation may be attributed to the formation of super zone boundary gaps, which alters the density of electronic states near the Fermi surface, where the variation of density of states also occurs in the vicinity of the Fermi level [40,41]. Similarly, a remarkable resistance change at the martensitic transition temeperature has also been found in Ni-Mn-Sn thin films and it is attributed to superzone boundary effects, which is caused by structural and magnetic superstructures [42].…”