Acoustic Energy Absorption in Ferromagnetic Ni-Mn-Ga Shape Memory Alloy Polymer Composites

The single crystal Ni-Mn-Ga and Ni-Mn-Ga particulate composites have responded to mechanical stress up to 1 kHz frequencies with significant acoustic attenuation. It has been observed that in Ni-Mn-Ga polymer composites, a heavy static load on both the ends of the system increases the acoustic stress amplitude and appears to have acoustic loss drops. The attenuation, as a function of frequency shows resonances in the displacement of the vibrating particle indicating the twin boundary motions. It is inferred that the resonances beyond the principal mode are highly damped in the Ni-Mn-Ga composite samples.