The evidence for the preferential orientation of Ni–Mn–Ga martensitic variants by compression or magnetic field was presented. The evolution of martensitic twinning configuration in Ni50Mn27.5Ga22.5 single crystal was optically observed initially under the applied compressive stress and then followed by the magnetic field. The magnetic field induced strain was measured at different conditions. The magnetic field induced strain was not observed in the original three-variant self-accommodated state. One percent of magnetic field induced strain was obtained after compression under 5MPa, attributed to a disappearance of the self-accommodated structure replaced by a two-variant structure. During magnetization, the favorable variants expand at the expense of others. After several cycles of compression and successive magnetization, a near single variant state and magnetic field induced strain of 5.5% were achieved in the rectangular single crystal. Forty-five degree macroscopic twin bands were observed during the magnetic field induced strain testing on (010) surface of an oriented rectangular sample with {100} faces.

Preferential Reorientation of Twin Variants in Ni–Mn–Ga Single Crystal. J.Wang, C.Jiang, H.Xu: Materials Science and Engineering A, 2006, 438-440, 1022-5