Application of Ferromagnetic Shape-Memory Alloys in Power Generation Devices
By the inverse magnetoplastic (IMP) effect, twin boundaries in magnetic shape memory alloys (MSMA) can be reoriented by applying a mechanical stress. The result of this applied stress is a plastic deformation, as well as a change of magnetization. Used in conjunction with a coil, this changing magnetic field was harnessed in a power generation device to produce an electrical signal. With the application of a static bias magnetic field, as well as the removal of the applied stress, the twin boundaries reoriented themselves and restored the transducer’s initial geometry. This process was repeated via a periodic force applied with a variable speed motor, and was performed at room temperature and with compact permanent magnets. A Ni-Mn-Ga MSMA single crystal with approximate dimensions 5.4 x 3.9 x 3.1 mm3 served as magnetomechanical transducer. Actuation frequencies up to 2.25 Hz were applied resulting in an output voltage of up to 3.8 mV and a power output of up to 80 nW.
Carpenter, D.; Chmielus, Markus; Rothenbühler, A.; Schneider, R.; and Müllner, Peter. (2009). "Application of Ferromagnetic Shape-Memory Alloys in Power Generation Devices". Proceedings of the International Conference on Martensitic Transformations ‘ICOMAT’08’, Santa Fe, NM, June 29-July 5, 2008, 365-369.