面内应变对外延生长Ni-Mn-Ga薄膜中7M马氏体变体数量的影响及其机理研究

外延生长Ni-Mn-Ga薄膜是微纳传感器和驱动器中的优选材料。外延生长Ni-Mn-Ga薄膜7M马氏体变体的数量是决定其能否获得大磁致应变性能的关键，且对薄膜所受的应变状态非常敏感。本项目拟利用（001）取向的PIN-PMN-PT基板制备外延生长Ni-Mn-Ga薄膜，研究施加电致应变对减少外延生长Ni-Mn-Ga薄膜7M马氏体变体数量的作用；利用晶体学计算分析描述电致应变作用下7M马氏体变体的演变过程，探讨面内应变对外延生长Ni-Mn-Ga薄膜7M马氏体变体数量的影响规律；阐明面内应变对减少外延生长Ni-Mn-Ga薄膜中7M马氏体变体数量的作用机理；最终获得由一个7M马氏体变体或者两个互为II型孪晶关系的7M马氏体变体组成的外延生长Ni-Mn-Ga薄膜，以期为外延生长Ni-Mn-Ga薄膜走向实用奠定理论和技术基础。

Epitaxial Ni-Mn-Ga thin films are the promising candidate materials for the magnetic controlled micro/nano sensors and actuators. The number of 7M martensite variants in epitaxial Ni-Mn-Ga thin films is the crucial for achieving large magnetic field induced strain. It is also sensitive to the strain status of epitaxial Ni-Mn-Ga thin films. In order to investigate the role of in-plane strain of the number of 7M martensite variants, the present work will employ (001) orientated PIN-PMN-PT monocrystal as the substrate for epitaxial Ni-Mn-Ga thin films. The evolution of 7M martenstie variant number under different electric field induced strain will be analyzed via the crystallographic calculation. Based on experimental results and crystallographic calculation, the mechanism of reduction of 7M martensite variant number by applying in-plane strain will be clarified. Finally, the epitaxial Ni-Mn-Ga thin film with one or two twin-related 7M martensite variants will be achieved. The investigation mentioned above would offer theoretical and technical fundaments for the application of epitaxial Ni-Mn-Ga thin films the magnetic controlled micro/nano sensors and actuators.