Effect of post-growth annealing and magnetic field on the two-way shape memory effect of Ni₅₂Mn₂₄Ga₂₄ single crystals

The effect of post-growth annealing and magnetic field on the two-way shape memory effect (TWSME) of Ni₅₂Mn₂₄Ga₂₄ single crystals was investigated. We found that samples subjected to a two-step post-growth annealing can provide a better TWSME than that of directly quenching from the parent phase. By way of comparison, the martensitic microstructures of samples, subjected to two different post-annealing treatments, were studied by means of optical and electron microscopy. Moreover, we found that the magnitude and direction of TWSME can be changed optionally by selecting the strength and direction of the magnetic field. The work output by the sample on a fixed magnetic field of 1.2 T was calculated to be 12 kJ m^-3, which is comparable to that of Terfenol-D actuators, being of order 10 kJ m^-3 reported by Clark et al (1988 J. Appl. Phys. 63 3910).