Microstructure and Properties of the Ferromagnetic Shape Memory Alloy Ni2MnGa

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

This research aims to get a better understanding of the interactions between the magnetic domain walls and the crystallographic intervariant boundaries as well as these aspects in various phases in shape memory alloys. The proposed study addresses the physical and magnetic microstructure and properties of Ni-Mn-Ga-Al alloys, with an emphasis on compositions with near room-temperature transformations. The magnetic microstructures are systematically investigated by means of Lorentz microscopy augmented by phase reconstruction techniques, and domain configurations are analyzed in terms of micromagnetics modeling efforts. Microstructural and micromagnetic observations are augmented by magnetic property measurements. Single crystals are grown at CMU and at the Naval Research Laboratory while polycrystalline bulk and thin film samples are produced at CMU. Thin films are grown by means of pulsed laser deposition techniques. Since magnetic actuation can provide large displacements with relatively simple driving circuitry, future actuator devices may include ferromagnetic shape memory films based on the NiMnGa alloy system. Educational efforts of the proposed program are directed towards the teaching of advanced materials characterization techniques, and involves website development (with the aid of undergraduate students) and the creation of a new course in collaboration with the University of Pittsburgh. %%% Magnetic actuator devices could potentially have a large impact on Micro Electro-Mechanical Systems (MEMS). Applications of ferromagnetic shape memory alloys in actuators will only be possible if an in-depth understanding of the microstructural and micromagnetic features is obtained. The primary goal of this research is to obtain such an understanding.