J. Phys. IV France 112 (2003) 1001
Pulsed field actuation of Ni-Mn-Ga ferromagnetic shape memory alloy single crystalM. Marioni, D. Bono, A.B. Banful, M. del Rosario, E. Rodriguez, B.W. Peterson, S.M. Allen and R.C. O'Handley
Massachusetts Institute of Technology, Office 13-5014, 77 Massachusetts Avenue, Cambridge, MA 02139, U.S.A.
Ferromagnetic Shape Memory Alloy Ni-Mn-Ga has twin boundaries in the martensitic phase that move when a suitable magnetic field is applied. In this fashion strains of up to 6% have been observed for static fields in single crystals . Recently 2.5% strain has been demonstrated  in Ni-Mn-Ga single crystals for oscillating fields up to frequencies of 75 Hz (150 Hz actuation). This work studies the actuation of single crystals when pulsed fields are applied. Fields in the 0.4-1.5MA/m-range were generated in an air coil with rise times of the order of 1ms and below. The elongation of the samples is measured with a light beam reflected off the tip of the crystal. Single twin boundaries have been observed to advance 0.16 mm during 600 sec-ong pulses. Actuation has been shown to be possible at least up to frequencies of 1700 Hz.
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