Superelastic response of Ni-Mn-Ga martensite in magnetic fields and a simple model

The irreversible and reversible straining (superplasticity and superelasticity) of the single crystal Ni_49.7Mn_29.1Ga_21.2 sample stressed compressively under a static magnetic field up to 1 T is described and successfully modeled. The sample possesses a five-layered martensitic structure at room temperature and it becomes almost fully superelastic (reversible strain close to 6%) for values of field higher than 0.3 T. The maximum sensitivity of the stress-strain curve to the magnetic field determined from the model is 6.8 MPa/T (7.2 MPa/T from measured data). Knowledge of magnetization curves of the single variant sample and stress-strain curve in zero magnetic field is sufficient to predict the stress-strain behavior in an arbitrary static magnetic field.