【作者】 李晓东；

【导师】 孙卓；

【作者基本信息】 华东师范大学 ， 凝聚态物理， 2008， 博士

【摘要】 磁致伸缩效应是指铁磁材料在外磁场的作用下,铁磁材料的长度或体积发生变化的现象,而超磁致伸缩效应的发现和进展更是在应用领域显示了重要价值。由于超磁致伸缩材料具有非常强的磁致伸缩效应、很高的机电耦合系数、较快的响应速度以及非接触式驱动等优点而倍受关注,已被广泛应用于声纳、大功率超声器、精密机械以及功能/结构材料等领域。本文从制备精确组分为Tb_0.27Dy_0.73Fe₂（Terfenol-D）薄膜和具有低场高灵敏度超磁致伸缩性能薄膜出发,制备了具有精确组分为Tb_0.27Dy_0.73Fe₂的[Tb/Fe/Dy]_n纳米多层膜和加入软磁层的[SL/Tb/Fe/Dy]_n纳米多层膜。并研究了该纳米多层膜的结构、磁性能和超磁致伸缩性能以及磁化过程对超磁致伸缩性能的影响。其主要结果如下:1.通过使用单质分离Tb、Fe、Dy靶材制备具有精确组分为Tb_0.27Dy_0.73Fe₂的[Tb/Fe/Dy]_n纳米多层膜,其性能如下:（1）通过X射线能谱仪（EDX）与电感耦合等离子体发射光谱仪（ICP-AES）测试表明两种不同条件下（室温条件和衬底温度300℃条件）制备的[Tb（2nm）/Fe（4nm）/Dy（3nm）]_n纳米多层膜的精确组分为Tb_0.27Dy_0.73Fe₂。（2） SEM形貌表明制备态下两种不同条件制备的[Tb/Fe/Dy]_n纳米多层膜都具有垂直多层膜平面的微观柱状结构。（3）对于室温条件下制备的[Tb/Fe/Dy]_n纳米多层膜有:a.[Tb/Fe/Dy]_n纳米多层膜在制备态和300℃温度退火处理后,仍旧为非晶态,纳米多层膜样品在退火温度高于400℃时开始有对应于立方Laves相的R-Fe₂的纳米晶出现,随着退火温度的升高,纳米晶粒逐步变大,并且有更多的Laves相晶体析出。b.M（o|¨）ssbauer谱和磁滞回线表明纳米多层膜样品的磁矩空间分布随着退火温度的升高而发生显著地变化。在制备态和退火温度为400℃时,纳米多层膜的磁矩空间取向为垂直面向分布,而在退火温度为300℃、500℃和600℃时,纳米多层膜磁矩的空间取向以面向分布为主。c.超磁致伸缩性能随着退火温度的升高,即纳米多层膜样品磁矩空间取向变化而变化。制备态和400℃退火处理后样品磁矩以垂直面向分布为主,超磁致伸缩难以达到饱和,样品超磁致伸缩性能随磁场的增大而近似线性增大:而300℃、500℃和600℃退火处理的纳米多层膜样品磁矩以面向分布为主,超磁致伸缩容易达到饱和。样品超磁致伸缩性能随外磁场的增大首先迅速增大,在磁场为0.32T下达到饱和。且在较低的磁场驱动下,远大于磁矩空间取向为垂直面向分布时的超磁致伸缩性能。（4）对于衬底加热300℃制备的[Tb/Fe/Dy]_n纳米多层膜有:a.衬底加热制备的纳米多层膜样品在制备态下就有立方Laves相的R-Fe₂的纳米晶析出。随着退火温度的升高,纳米晶粒尺寸逐步变大。b.磁滞回线表明,衬底加热制备的纳米多层膜样品在退火处理温度低于400℃时,磁矩的空间取向以垂直面向分布为主。在退火温度为500℃和600℃时,磁矩的空间取向以面向分布为主。c.衬底加热的纳米多层膜样品的超磁致伸缩性能也随着磁矩的空间取向而发生变化。（5）衬底加热条件下制备的纳米多层膜比室温条件下制备的纳米多层膜具有更优越的超磁致伸缩性能和低场下的超磁致伸缩灵敏度。（6）磁化过程与超磁致伸缩性能的关系也证明了超磁致伸缩性能与磁矩的空间取向密切相关。2.加入软磁层的[SL/Tb/Fe/Dy]_n纳米多层膜的性能如下:（1）对于室温条件下制备的[Fe/Tb/Fe/Dy]_n纳米多层膜样品,纳米多层膜样品在制备态和300℃退火处理,仍旧处于非晶态;在退火温度为400℃时,开始出现R-Fe₂相和α-Fe相的纳米晶;随着退火温度的逐步升高,晶粒逐渐长大,在600℃退火处理后,纳米多层膜样品基本完全晶化。磁滞回线表明,由于软磁层的加入,使得纳米多层膜样品的磁性能有了显著提高,磁矩分布以面向分布为主,矫顽力变小而饱和磁化强度增大。软磁层Fe的加入使得超磁致伸缩性能也有大幅度的提高,饱和磁场降低为0.25T,并且比[Tb/Fe/Dy]_n纳米多层膜具有更好低场灵敏度。（2）对于室温条件下制备的[FINEMET/Tb/Fe/Dy]_n纳米多层膜样品,由于FINEMET合金薄膜比Fe薄膜具有更大的饱和磁化强度和更小的矫顽力,因而超磁致伸缩性能较加入Fe薄膜的纳米多层膜有显著的提高,且饱和磁化强度减小为0.19T。（3）衬底温度300℃制备的纳米多层膜样品在制备态下就有α-Fe相和R-Fe₂相的纳米晶出现。300℃退火处理,并没有改变纳米多层膜样品的结构。随着退火温度的升高,晶粒的逐步变大,并且有更多的α-Fe相和R-Fe₂相的纳米晶析出。磁滞回线表明,纳米多层膜样品的矫顽力随着退火温度的升高而变小,而饱和磁化强度随退火温度的升高而增大。超磁致伸缩性能随退火温度的升高而变大。更多还原

【Abstract】 The magnetostriction effect can be described most generally as the deformation of a body in response to a change in an external magnetic field.The discovery of giant magnetostriction（GMS） and the progress in this field have demonstrated its important value in applications.The Terfenol-D GMS thin films have high electronic resistivity,high magnetic permeability,low magnetic hysteresis,and weak magnetocrystalline anisotropy.The GMS films with low field sensitivity are useful to the new type electro-mechanical transformation system.In this work,we developed a simple way to prepare [Th/Fe/Dy]_n nano-multilayer film with precise composition of Tb_0.27Dy_0.73Fe₂ and insert soft layer[SL/Tb/Fe/Dy]_n nano-multilayer film with low field GMS sensitivity. Meanwhile,the structure,magnetic properties and giant magnetostriction of the nano-multilayer films are studied.And the main contents and results are as follows:1.Pure element targets Tb,Dy and Fe were used to deposit with precise composition[Th/Fe/Dy]_n nano-multilayer films.（1） The compositions of[Tb（2nm）/Fe（4nm）/Dy（3nm）]_n nano-multilayer film was analyzed by energy dispersive analysis system of X-ray（EDX） and inductively coupled plasma atomic emission spectroscopy（ICP-AES）.The analyzed composition of nano-multilayer film was(Tb_0.27Dy_0.73) Fe₂.（2） SEM measurement shows that the morphology and microstructure of those two as deposited nano-multilayer films have columnar structures consisting of grains oriented perpendicularly to the film plane.（3） The[Tb/Fe/Dy]_n nano-multilayer films were deposited at room temperature.a.The as deposited nano-multilayer film and nano-multilayer films annealed at temperature 300℃are still in amorphous state.At the annealing temperature of 400℃,the R-Fe₂ grains begin to be segregated from the amorphous matrix. b.The M（o｜¨）ssbauer spectrum and the magnetic hysteresis loops show that the magnetic moments distributed orientation of nano-multilayer films are changed by the annealing temperature.In as deposited state and annealed temperature of 400℃,magnetic moments distributed orientation of nano-multilayer films is perpendicular to the film plane;yet at annealing temperature of 300℃、500℃and 600℃,magnetic moments distributed orientation of nano-multilayer films is in random.c.Because nano-multilayer films（in as deposited state and annealing temperature at 400℃） have perpendicular anisotropy,i.e.,the magnetic domains distributed orientation is perpendicular to the film plane.When the external field is parallel to the film plane,the magnetic field can not magnetize the magnetic moments freely,so the GMS increases almost linearly in the applied field.When the magnetic domains distributed orientation of nano-multilayer films（annealed temperature of 300℃、500℃and 600℃） is in random,the GMS of these nano-multilayer films increases rapidly at first and then almost saturates at the external filed of 0.32T.（4） The[Tb/Fe/Dy]_n nano-multilayer films were deposited at 300℃substrate temperature.a.The R-Fe₂ nano-grains begin to be segregated from the amorphous matrix in as deposited nano-multilayer film.b.When the annealed temperature lower than 400℃,the magnetic domains distributed orientation is perpendicular to the film plane;when the annealed temperature higher than 500℃,the magnetic domains distributed orientation is parallel to the film plane.c.The GMS of the nano-multilayer films is also determined by the magnetic moments distributed orientation.（5） The GMS value in nano-multilayer films deposited at 300℃substrate temperature was higher than those nano-multilayer films deposited at room temperature. （6） The huge influence of the magnetic anisotropy on the field dependence of the magnetostriction is considered by different types of magnetization processes.2.The insert soft layer[SL/Tb/Fe/Dy]_n nano-multilayer films combine the giant magnetostrictive materials（[Tb/Fe/Dy]_n） and materials with large magnetic polarizations（Fe and FINEMET）.（1） Because of the interaction between the soft layer and the GMS layer,the [SL/Tb/Fe/Dy]_n nano-multilayer film has low saturation magnetization, high GMS performance and lower coercivity,and the magnetic domains distributed orientation is parallel to the film plane.（2） The[Fe/Tb/Fe/Dy]_n nano-multilayer films in as deposited state and annealed at temperature 300℃are still in amorphous state.At the annealing temperature of 400℃,theα-Fe and R-Fe₂ grains begin to be segregated from the amorphous matrix.Because of the interaction between the soft layer Fe and the GMS layer,the magnetic moments distributed orientation of all[Fe/Tb/Fe/Dy]n nano-multilayer films are paralleled to the film plane;and all[Fe/Tb/Fe/Dy]_n nano-multilayer films have lower coercive force,higher saturated magnetic magnetization intensity and better low field GMS performance.（3） Because the soft magnetic properties of FINEMET layer are much than those of Fe layer,the GMS performance of[FINEMET/Tb/Fe/Dy]_n nano-multilayer films are higher than that of[Fe/Tb/Fe/Dy]_n nano-multilayer films.（4） The[Fe/Tb/Fe/Dy]_n nano-multilayer films were deposited at 300℃substrate temperature.Theα-Fe and R-Fe₂ grains begin to be segregated from the amorphous matrix at the as deposited nano-multilayer film.The magnetic hysteresis loops show that the coercive force decreases and the saturated magnetization intensity increases by increasing annealing temperature.更多还原