Uniaxial-stress tuned large magnetic-shape-memory effect in Ni-Co-Mn-Sb Heusler alloys

摘要

Combined strain and magnetization measurements on the Heusler shape-memory alloys Ni_(45)Co_5Mn_(38)Sb_(12) and Ni_(44)Co_6Mn_(38)Sb_(12) give evidence for strong magneto-structural coupling. The sample length changes up to 1 % at the martensitic transformation, between a ferromagnetic, austen-itic phase at high temperatures and a weakly magnetic, low-symmetry martensitic phase at lower temperatures. Under moderate uniaxial stress, the change in the sample length increases to and saturates at about 3%, pointing to stabilization of a single martensitic variant. A reverse martensitic transformation can also be induced by applying magnetic field: we find that within the temperature range of thermal hysteresis of the martensitic transformation, applying a field can induce a metasta-ble expansion of the sample, while at slightly lower temperatures, the field response is reversible. These findings provide key information for future use of Ni(Co)-Mn-Sb-based Heusler compounds in, e.g., actuators and mechanical switches.