11 July 2002 Pulsed magnetic field actuation of single-crystalline ferromagnetic shape memory alloy Ni-Mn-Ga
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Abstract
Ferromagnetic shape memory alloys can exhibit magnetic-field-induced strains of several percent at room temperature. These strains have been shown to correlate with the motion of twin boundaries in the crystals. Twin boundaries advance by the motion of stacking faults along the twin boundary. Such mechanical defects have as an upper limit of their velocity, the speed of sound. It is an important matter to understand the mobility of twin boundaries in ferromagnetic shape memory alloys from a scientific perspective. Namely, how does their velocity depend on field strength, crystal structure and perfection, what are the roles of inertia and threshold field, and does the velocity ever approach anything like the speed of sound. From a practical point of view, it is important to know the twin boundary dynamics in order to understand the bandwidth capabilities of these new active materials as well as their response to different field wave forms that may optimize the response for particular applications. In the present paper we describe a pulse field experimental setup and preliminary results that begin to address the issues raised above.
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Miguel A. Marioni, David Bono, Robert C. O'Handley, Samuel M. Allen, "Pulsed magnetic field actuation of single-crystalline ferromagnetic shape memory alloy Ni-Mn-Ga", Proc. SPIE 4699, Smart Structures and Materials 2002: Active Materials: Behavior and Mechanics, (11 July 2002); doi: 10.1117/12.474975; https://doi.org/10.1117/12.474975
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