Effect of Surface Treatment on the Switching Field of Ni-Mn-Ga

Ni-Mn-Ga is a Magnetic Shape Memory (MSM) alloy, which changes shape when either a mechanical stress or magnetic field exceeds the twinning stress or switching field, respectively, allowing for twin boundary motion and the alloy deforms. Deforming by mechanical and magnetic means affects fatigue life of these alloys. Fatigue life improves by using surface treatments to reduce the size and number of twins inside the alloy. With good surface treatments, the fatigue life increases thousand-fold. Fatigue life is important to MSM alloys because this material finds application in actuators such as in micro-pumps. In this study, we identified the magnetic switching field, i.e. the magnetic field that triggers twin boundaries to move, as the primary metric to study the effectiveness of various surface treatments. Vibrating Sample Magnetometry (VSM) measures the switching field of different samples that are taken from different locations in one crystal. The next step of this study is to collect data of how different methods of surface treatment affect the surface roughness, switching field, and fatigue life of the alloy