Magnetic field-enhanced shape memory effect in Ni_(51.6)Mn_(23.4)Ga_(25) single crystals

摘要

We have performed the various measurements of the transformation strain with and without the different external magnetic fields on the Ni_(51.6)Mn_(23.4)Ga_(25) single crystals. A stress-free and two-way thermoelastic shape memory, with -1.15% strain (negative sign represents the shrinkage) and 6 K temperature hysteresis, has been found in the single crystal. The deformation can be enhanced up to -2.35% with a bias field 1.2 T applied along the measurement direction of the parent phase [001] cry stallographic axial direction. Turning the field laterally applied to [010] and [ 100] directions of the parent phase, however, the strain was suppressed by the field of 1.2 T to 0.56% and -0.55%, respectively, a different deformation scene. Moreover, it is found that even the field of 1.2 T does not have a significant influence on the phase transition temperature and the temperature hysteresis, which indicates that the mechanism of field-enhanced strain in this material is the twin boundary motion.