Breaching the work output limitation of ferromagnetic shape memory alloys

One important parameter that quantifies the performance of ferromagnetic shape memory alloys is the blocking stress. To date, the low blocking levels (< 5 MPa) impede the utilization of these alloys in applications where high work output is required. In this paper, we demonstrate an increase in the blocking stress by more than 100% by reducing the actuator size. A new theoretical model shows that smaller specimens have increased values of the blocking stress due to an enhancement in the energy barrier to magnetization rotation and indicates on a fundamental relationship among the specimen size, its microstructure, and its physical properties. (C) 2008 American Institute of Physics.