Sensing behavior of ferromagnetic shape memory Ni-Mn-Ga

Due to their large magnetic field induced strains and fast response potential, ferromagnetic shape memory alloys have mainly been studied from the perspective of actuator applications. This paper presents characterization measurements on a commercial Ni-Mn-Ga alloy with a goal to investigate its feasibility as a deformation sensor. Experimental determination of flux density as a function of quasistatic strain loading and unloading at various fixed magnetic fields gives the bias field needed for maximum recoverable flux density change. This bias field is shown to mark the transition from irreversible (quasiplastic) to reversible (pseudoelastic) stress-strain behavior. A reversible flux density change of 145 mT is observed over a range of 5.8 % strain and 4.4 MPa stress at a bias field of 368 kA/m. The alloy investigated therefore shows potential as a high-compliance, high-displacement deformation sensor.