Microstructure and Properties of the Ferromagnetic Shape Memory Alloy Ni2MnGa

本研究旨在更好地了解形状记忆合金不同相中磁畴壁与晶体变相边界之间的相互作用以及这些方面。提出的研究解决了Ni-Mn-Ga-Al合金的物理和磁性组织和性能，重点是近室温转变的成分。利用相重建技术增强的洛伦兹显微镜系统地研究了磁性微结构，并根据微磁建模工作分析了畴组态。显微结构和微磁观测是由磁性测量增加的。单晶在CMU和海军研究实验室生长，而多晶体和薄膜样品在CMU生产。利用脉冲激光沉积技术生长薄膜。由于磁致动可以用相对简单的驱动电路提供大的位移，未来的致动器装置可能包括基于NiMnGa合金系统的铁磁形状记忆膜。拟议项目的教育工作是针对先进材料表征技术的教学，包括网站开发（在本科生的帮助下），以及与匹兹堡大学合作开设新课程。磁致动器装置可能对微机电系统（MEMS）产生巨大影响。只有对铁磁形状记忆合金的微观结构和微磁特性有深入的了解，铁磁形状记忆合金在执行器中的应用才有可能。本研究的主要目标就是获得这样的认识。

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.