Actuation field in martensitic Ni_(49.0)Mn_(23.5)Ga_(27.5)

摘要

The singular point detection technique has been applied to determine the magnetic anisotropy constant K_1 of small martensitic Ni_(49.0)Mn_(23.5)Ga_(27.5) (wt %) single crystals with a martensitic transformation temperature T_M of 276 K. As expected, K_1 increases with decreasing temperatures below T_M, following a magnetization power law K_1(T)/K_1(0)=[M_s(T)/M_s(0)]~3. At 5 K, K_1 reaches 3.24 X 10~5 J/m~3. The force required to initiate twin boundary motion increases exponentially with decreasing temperature. The combination of both temperature dependences leads to a very restricted temperature window for magnetic actuation using this alloy.