Kinetic Arrest of Martensitic Transformation in NiCoMnAl Metamagnetic Shape Memory Alloy

Magnetic properties and martensitic transformation behaviors of NiCoMnAl metamagnetic shape memory alloys were investigated. The kinetic arrest phenomenon was observed at about 40 K during thermomagnetization measurements. At temperatures ranging from 4.2 to 200 K, magnetic field-induced reverse transformation was confirmed by a pulse magnetometer with a magnetic field up to 45 T. By plotting the equilibrium magnetic fields against the measured temperature, the transformation entropy change was calculated by using the Clausius-Clapeyron equation. The transformation entropy change was found to become zero below 40 K, which can explain the appearance of the kinetic arrest phenomenon. [doi: 10.2320/matertrans.M2010098]