Anomaly of critical stress in stress-induced transformation of NiCoMnIn metamagnetic shape memory alloy

Abstract

Stress-induced martensitic transformation below room temperature for a Ni45Co5Mn36.1In13.9 single-crystal, in which no martensitic transformation occurs during cooling down to 4.2 K under zero stress, was investigated by using compression test. The equilibrium stress estimated from the critical stresses in stress-induced forward and reverse transformations decreased with decreasing temperature, while it became almost constant at temperatures below about 140 K. This anomaly can be explained by the abnormal temperature dependence of the transformation entropy change, which has also been detected by magnetization measurement.