The properties and applications of magnetostrictive rare-earth compounds

The exceptional magnetoelastic properties of rare-earth iron compounds (Terfenol) offer great potential for a variety of applications. Different techniques for the characterisation of their magnetoelastic performance have been developed which provide consistent data, for instance, for the magnetomechanical coupling efficiency. Measurements have been made of the field and pressure dependencies of the magnetomechanical coupling (k33), magnetostrictive strain (λ) and magnetostrictive strain coefficient (d33), so delineating the material's optimum operating conditions for use in Terfenol actuators. A self-adaptive variable structure controller has been designed to cater for variations in actuator response which arise from dynamic loading. (orig.)