Intrinsic position sensing of a Ni-Mn-Ga microactuator

This paper presents an investigation of the intrinsic magnetoresistance of a ferromagnetic shape memory alloy microactuator for position sensing. The microactuator is designed as a double-beam cantilever made of a polycrystalline Ni-Mn-Ga thin film, which exhibits both a martensitic transformation in the temperature range 333-359K and a ferromagnetic transition at about 370K. The microactuator is placed in the inhomogeneous magnetic field of a miniature Nd-Fe-B magnet causing a mixed thermo-magnetoresistance effect upon actuation. The maximum in-plane magnetic field is about 0.38T. In this case, the maximum magnetoresistance is 0.19%. Under these conditions, a maximum positioning accuracy of 18νm can be reached within the deflection system presented.