The crystallization kinetics of Co doping on Ni-Mn-Sn magnetic shape memory alloy thin films

Co doping is an effective means to improve the performance of Ni-Mn-Sn alloy bulks and thin films. However, the Co doping effect on the crystallization process of the Ni-Mn-Sn alloy thin films is important but not clear. Therefore, we investigate the influence of Co doping on the crystallization kinetics for Ni₅₀Mn_37- Sn₁₃Co (x = 0, 0.5, 1.5, 4) magnetic shape memory alloy thin films by DSC analysis. For the non-isothermal process, each DSC curve has a single exothermic peak, which is asymmetrical. The crystallization peak temperatures and the activation energy of thin films both rise gradually with increasing Co content. Then, the activation energy of Ni₅₀Mn_37- Sn₁₃Co (x = 0, 0.5, 1.5, 4) thin films obtained by the Kissinger equation method is determined as 157.9 kJ mol^-1, 198.8 kJ mol^-1, 213 kJ mol^-1 and 253.6 kJ mol^-1, respectively. The local activation energy of thin films with different Co content show the different variation tendency. In the isothermal crystallization, the average of the Avrami exponent n for thin films of each Co content is approximately 1.5, suggesting that the mechanism of crystallization is two-dimensional diffusion-controlled growth for Ni₅₀Mn_37- Sn₁₃Co (x = 0, 0.5, 1.5, 4) thin films.