In situ optical microscopic observation of NiCoMnIn metamagnetic shape memory alloy under pulsed high magnetic field

In situ microscopic imaging observation was performed on Ni45Co5Mn36.7In13.3 metamagnetic shape memory alloy. Magnetic field-induced reverse martensitic transformation and heating-induced martensitic transformation were directly observed for the first time. The fraction of martensite phase was evaluated by contrast change from micrographs and critical magnetic fields were determined. Isothermal growth of martensite after magnetic field application was also observed. Comparison between the micrographs after the application of a magnetic field and on cooling also revealed the nature of the adiabatic process under a strong driving force.