【作者】 蒋洪川；

【导师】 李言荣；

【作者基本信息】 电子科技大学 ， 材料物理与化学， 2006， 博士

【摘要】 巨磁致伸缩薄膜在微泵、微阀、微开关等MEMS系统以及微型器件中有着广阔的应用前景。本论文以提高TbFe薄膜的低场磁致伸缩性能为主要研究目标，利用TbFe₂磁致伸缩相和α-Fe软磁相纳米晶交换耦合效应降低TbFe薄膜的饱和场，进而提高TbFe薄膜的低场磁致伸缩性能。主要开展了薄膜磁致伸缩系数测试系统发计和构建、非晶态TbFe磁致伸缩薄膜的制备及性能研究、α-Fe／TbFe₂纳米晶交换耦合一维模型的建立，以及快速循环退火对TbFe薄膜磁致伸缩性能的影响等几个方面的系统研究。根据材料力学原理对磁致伸缩薄膜-基片悬臂梁结构进行了分析，推导得到了薄膜磁致伸缩系数与悬臂梁自由端挠度的关系式。基于激光光杠杆放大法，实现了薄膜磁致伸缩系数的计算机辅助测试。通过标定，测试系统的分辨率小于1ppm。采用磁控溅射法制备非晶TbFe薄膜，系统研究了Ar分压和溅射角度对TbFe薄膜微结构、磁性能以及磁致伸缩性能的影响。研究结果表明：随Ar分压的增大，TbFe薄膜中Tb含量增加，薄膜的磁畴结构由垂直于膜面逐渐转向平行于膜面，薄膜的垂直各向异性逐渐减小，面内各向异性逐渐增强。在适当的Ar分压范围内，Ar分压的增加有利于改善薄膜的软磁性能，提高薄膜的低场磁致伸缩性能。倾斜溅射可显著改善TbFe薄膜的软磁性能，提高薄膜的低场磁致伸缩性能。随溅射角度的减小，TbFe薄膜的软磁性能逐渐提高、饱和场逐渐降低、低场磁致伸缩性能逐渐提高。基于能量最小原理，首次建立了α-Fe／TbFe₂纳米晶交换耦合一维模型，采用微磁学方法深入分析了α-Fe／TbFe₂纳米晶交换耦合作用、α-Fe磁各向异性角、软磁相磁晶各向异性常数以及晶粒尺寸对TbFe薄膜磁性能以及磁致伸缩性能的影响。模拟结果表明：与单一的TbFe₂相相比，α-Fe／TbFe₂纳米晶交换耦合效应可显著改善TbFe薄膜的软磁性能，提高TbFe薄膜的低场磁致伸缩性能；α-Fe的磁各向异性角对TbFe薄膜的性能几乎没有影响；软磁相磁晶各向异性常数的减小，有利于TbFe薄膜软磁性能的改善，有利于提高TbFe薄膜低场磁致伸缩性能；α-Fe和bFe₂相晶粒尺寸显著影响TbFe薄膜的性能，在交换耦合尺度范围内，随晶粒尺寸的增大，TbFe薄膜的软磁性能提高，在低场下，TbFe薄膜的磁致伸缩性能提高，而高场下，TbFe薄膜的磁致伸缩性能却降低。首次从理论上解释了α-Fe／TbFe₂纳米晶交换耦合效应可提高TbFe薄膜的低场磁致伸缩性能。系统研究了快速循环退火对TbFe₂和α-Fe纳米晶相的形成、TbFe薄膜微结构、磁性能以及磁致伸缩性能的影响。研究表明：在一定的温度和时间范围内，快速循环退火可在TbFe薄膜中获得纳米晶TbFe₂磁致伸缩相和α-Fe软磁相；在交换耦合尺度范围内，TbFe₂磁致伸缩相和α-Fe软磁相纳米晶交换耦合效应可显著改善TbFe薄膜的软磁性能，提高TbFe薄膜的低场磁致伸缩性能，实验研究结果与理论研究结果定性吻合。首次从实验上证实了α-Fe／TbFe₂纳米晶交换耦合效应可提高TbFe薄膜的低场磁致伸缩性能。本论文得到的制备TbFe薄膜优化工艺参数为：Ar分压0．6Pa，溅射功率80W，靶基距70mm，溅射角度15°，退火温度550℃，退火时间240s，升温速率50℃／s。采用优化工艺制备的TbFe薄膜在外场为16kA／m时，薄膜的磁致伸缩系数为280ppm。更多还原

【Abstract】 Giant magnetostrictive films can be widely used in MEMS and micromagnetic devices, such as micro-pumps, micro-valves, micro-switches. In this dissertation, the nano-crystalline exchange-coupling effect of TbFe₂ magnetostrictive phase andα-Fe soft magnetic phase was utilized to reduce TbFe film saturation field, and then to improve TbFe film low magnetic field magnetostriction. Thus, the design and realization of film magnetostrictive coefficient （λ） measuring system, the preparation of amorphous TbFe films, the establishing ofα-Fe/TbFe₂ nano-crystalline exchange-coupling one dimension model, and the influences of the rapid recurrent thermal annealing on TbFe film magnetostriction were investigated systematically. The main results are as follows:Firstly, based on the material mechanical principles, the magnetostrictive film-substrate cantilever was analysised. The formula of magnetostrictive coefficient and cantilever deflection is deduced. Then, based on the laser cantilever deflection method, the film magnetostrictive coefficient measuring system was designed and realized. By calibration, the error of the measuring system is within 1ppm.Secondly, amorphous TbFe films were prepared by magnetron sputtering. The influences of argon partial pressure and sputtering angles on TbFe film micro-structures, magnetic and magnetostrictive performances were investigated systematically. With the increase of argon partial pressure, the content of Tb in the as-deposited TbFe films increases. With the increase of argon partial pressure, the magnetic easy direction of the films gradually changes from perpendicular direction to parrallel to the film plane. Within a certain argon partial pressure region, the increase of the argon partial pressure can improve the in-plane soft magnetic performances of the samples, and then improve film low magnetic field magnetostriction. The in-plane magnetostriction characteristics at lower magnetic field can be greatly improved by the oblique sputtering technique. With the decrease of deposition angles, the easy magnetization directions of the films can be gradually changed from perpendicular to in the film plane, and the in-plane magnetostriction also increases at lower magnetic field. Thirdly, the one dimension model of a-Fe/TbFe2 nano-crystalline exchange-coupling was established by the free energy functional minimization. Based on the model, the influences ofα-Fe/TbFe₂ nano-crystalline exchange-coupling effect, magnetic anisotropy angles ofα-Fe, magneto-crystalline anisotropy constants of soft magnetic phase and grain sizes on TbFe film magnetic and magnetostrictive performances were simulated. The results show that theα-Fe/TbFe₂ nano-crystalline exchange-coupling effect can improve the TbFe film soft magnetic properties, and thus improve film low field magnetostriction. However, the influences of magnetic anisotropy angles ofα-Fe can be ignored. With the decrease of magneto-crystalline anisotropy constants of soft magnetic phase, the soft magnetic performances of TbFe films are improved, then the low magnetic field magnetostriction is increased. The grain size plays an important role in the influences on the magnetic and magnetostrictive performances of TbFe films. Within the exchange-coupling length, with the increase of grain size of TbFe₂ andα-Fe, the magnetostriction of TbFe films increases at lower magnetic field, however, it decreases at larger magnetic field.Fourthly, the influences of rapid recurrent thermal annealing on TbFe film magnetostriction were investigated systematically. The results show that TbFe₂ andα-Fe nano-crystalline can be formed in TbFe films within a certain annealing temperature and time region. Within the exchange-coupling length, the nano-crystalline exchange-coupling effect of TbFe₂ andα-Fe can improve TbFe film soft magnetic performances, and then improve film low field magnetostriction. The experimental results agree with the micromagnetic simulations very well.The optimal preparing process parameters of TbFe films are as followings: 0.6Pa of argon partial pressure, 80W of sputtering power, 70mm of target-substrate distance, 15°of sputtering angels, 550℃of annealing temperature,240 seconds of annealing time and 50℃/s of heating rate. The magnetostriction of the films prepared by this optimal preparing process can reach 280ppm at the static magnetic field of 16kA/m.更多还原