Tailored Magneto-Mechanical Response in Ni-Mn-Ga Magnetic Shape Memory Single Crystals

We show on a Ni-Mn-Ga magnetic shape memory alloy that the magneto-mechanical response (actuating performance) of an MSM single crystal is significantly influenced by the martensite twin microstructure of the crystal. We demonstrate examples of the mechanical and magneto-mechanical responses of single crystals with the following twin microstructures: i) single variant ii) single twin boundary iii) fine twins. We show that a single twin boundary exhibits a sharp actuating response in a small magnetic field whereas fine twins exhibit a more gradual response and a larger magnetic field has to be applied to achieve actuation. The suitability of the studied microstructures for use in a magnetic actuator is discussed.