Phase diagram and composition optimization for magnetic shape memory effect in Ni-Co-Mn-Sn alloys

The composition dependent phase transformation and magnetic properties of the Ni 50 − x Co x Mn 39 Sn 11 ( 0 ≤ x ≤ 10 ) alloys were systematically investigated. Based on the obtained results, the phase diagram of this alloy system was established. Considering the combination of large magnetization difference across phase transformation Δ M and small transformation entropy change Δ S , the optimal composition range of 5 ≤ x ≤ 8 for magnetic-field-induced phase transformation (MFIPT) and consequently magnetic shape memory effect was figured out. Furthermore, the decrease in martensitic transformation temperatures by magnetic fields and almost fully reversible MFIPT from martensite to austenite were confirmed in the alloys within this composition range.