【作者】 郑富；

【导师】 魏福林；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2012， 博士

【摘要】 随着电子信息产业的飞速发展,迫切要求电子元件向小型化,高频化与集成化的方向发展,这对作为电子元件核心的磁性材料提出了更高的要求。目前,由于软磁薄膜在高集成器件(如磁性传感器、变压器以及磁记录用磁头材料)中具有潜在的应用价值而受到研究人员的广泛关注。对于这些软磁薄膜的基本要求是具有高的饱和磁化强度(4πMs),低的矫顽力(Hc),高的电阻率(ρ)以及合适的各向异性场(Hk)。在这些材料中,FeCo合金因其具有高的饱和磁化强度而成为一种优势材料。但FeCo合金薄膜具有高的磁晶各向异性以及高的饱和磁致伸缩系数,难以获得良好的软磁特性和面内单轴磁各向异性。因而,改善FeCo合金薄膜的软磁特性与高频响应是一项重要而有意义的工作。在本论文中,我们通过第三方元素添加的方法制备了一系列的FeCo基合金薄膜。分别研究了这些薄膜的静态与动态磁性。主要结论如下：Ⅰ. FeCoAlO与FeCoAlN薄膜对FeCoAlO与FeCoAlN薄膜,通过Al2O3与AlN陶瓷片引入Al-O与Al-N元素,成功实现了FeCo合金薄膜的磁性软化。在两种薄膜中,良好的软磁特性均来源于晶粒的细化。磁导率谱线基本表现为弛豫型谱线特征,在低频区间,磁导率的实部μ具有较高的值。(1)随着Al含量的增加,FeCoAlO薄膜表现出良好的软磁特性,在Al含量为11.8at.%到18.5at.%变化时,薄膜具有低的矫顽力(3-6Oe)。这些薄膜具有明显的面内单轴磁各向异性(Hk在50Oe左右),当Al含量为11.8at.%时,薄具有高的饱和磁化强度(4πMs=21.1kG)与低的矫顽力(Hce=5.2Oe,Hch=3.6Oe)。(2)随着Al含量的增加,FeCoAlN薄膜同样表现出良好的软磁特性,当Al含量从13.8at.%变化到31.0at.%时,薄膜具有低的矫顽力(5-8Oe)。当Al含量为21.9与28.8at.%时,薄膜面内的各向异性发生变化。Ⅱ. FeCoAlO梯度膜为了获得良好的高频特性,我们通过A1203陶瓷片摆放在合金靶溅射环的一侧,制备了FeCoAlO成分梯度膜。(1)通过使用这种不均匀靶,将Al-O成分梯度引入FeCoAlO薄膜,诱导出应力各向异性。与成分均匀的薄膜相比,梯度膜具有优异的高频特性。(2)A1203陶瓷片的添加量使得FeCoAlO梯度膜的磁谱曲线表现出三种不同的特性：弛豫型特性(4,8pcs),共振型特性(12,16pcs)以及在GHz频段的吸收特性(20,24pcs)。(3) FeCoAlO梯度膜在Ar气流量为7.5-15sccm时,具有非常高的共振频率(>3.0GHz),并且在低频区间磁导率的实部μ具有较高的值(-200),特别地,当Ar气流量为15sccm时,共振频率为4.0GHz。当Ar气流量等于或大于12.5sccm时,薄膜的易磁化轴垂直于外加磁场的方向。(4) FeCoAlO梯度膜在将外加磁场去掉时,仍然具有良好的高频响应。(5)溅射气压为在4-12mTorr变化时,薄膜均具有大的面内单轴磁各向异性(Hk>100Oe)。Ⅲ. FeCoAlON与FeCoZr条形畴薄膜我们研究了具有条形畴结构的FeCoAlON与FeCoZr薄膜的静态与动态磁性。条形畴的出现需要达到一定的元素添加量,薄膜的厚度必须大于一个临界值。对两种类型的条形畴薄膜,磁谱曲线均表现为多峰共振。(1)在210nm的FeCoAlON薄膜(氮分压为5%)与150nm的FeCoZr薄膜(Zr含量为11.2at.%)中观察到了条形畴的出现,这个厚度分别为两种薄膜的临界厚度。(2)对具有条形畴结构的薄膜,面内磁滞回线的剩磁比能够体现出磁矩与膜面偏离角度的大小。剩磁比越小,薄膜的磁矩偏离膜面的角度越大,垂直磁各向异性越明显。更多还原

【Abstract】 With the rapid development of electronics and information industry, the electronic components are urgently required to the direction of the miniaturization, high-frequency, and integrated. As the core of electronic components, magnetic materials are put forward higher requirements. Nowadays, Soft magnetic thin films have been studied intensively because of their potential applications in highly integrated devices, such as magnetic inductors, transformers, and magnetic recording heads. The basic demands for these films are high saturation magnetization4nMs, low coercivity Hc, high electric resistivity p, and appropriate anisotropy field Hk. Among various materials, FeCo alloys are important materials for their high saturation magnetization. However, it is difficult for FeCo alloys thin fims to achieve low coercivity and in-plane uniaxial magnetic anisotropy due to its high magnetocrystalline anisotropy and saturation magnetostriction constant. Therefore, it is important and essential to improve the soft magnetic properties and high-frequency characteristics of the FeCo alloy thin films.In this thesis, a series of FeCo based alloy thin films were prepared by adding third element. The static and dynamic properties of these films were investigated, respectively. The main conclusions are as follows:Ⅰ. FeCoAlO and FeCoAlN thin filmsFor FeCoAlO and FeCoAIN thin films, the Al-O and Al-N elements added by using Al2O3and AlN ceramic chips could successfully optimize the soft magnetic properties of FeCo alloy thin films. The good soft magnetic properties can be attributed to the refine of grain size in both kinds of the films. The permeability spectra almost exhibited a relaxation characteristic and the real part of the permeability,μ’,had a high value at low frequency region.(1) FeCoAlO thin films showed good soft magnetic properties with increasing of Al content. As the Al content changed from11.8to18.5at.%, a low coercivity Hc of3-6Oe was obtained. These films possessed a well defined in-plane uniaxial magnetic anisotropy(Hk～50Oe). When the Al content was11.8at.%, the film showed high saturation magnetization (4nMs=21.1kG) and low coercivity (Hce=5.2Oe, Hch=3.6Oe Hc).(2) FeCoAlN thin films also showed good soft magnetic properties with increasing of Al content. As the Al content changed from13.8to31.0at.%, a low coercivity Hc of5-8Oe was obtained. The in-plane anisotropy of the film changed while the Al content was21.9and28.8at.%.Ⅱ. FeCoAlO gradient composition thin filmsIn order to get good frequency performance, the FeCoAlO gradient composition thin films fabricated by composite target with Al2O3ceramic chips arrayed in one half of sputtering area were introduced.(1) By using the asymmetric target, the Al-O composition gradient was introduced into the FeCoAlO thin films to induce the stress anisotropy. The excellent high frequency characteristics of the gradient composition thin films were much improved compared with that of the uniform composition thin films.(2) The permeability spectra of the FeCoAlO gradient composition films exhibited three different features with the number of the Al2O3ceramic chips: relaxation characteristic (4,8pcs), resonance characteristic (12,16pcs), and absorptive characteristic in GHz region (20,24chips).(3) The FeCoAlO gradient composition films showed very high resonance frequency of beyond3.0GHz at Ar gas flow rate of7.5-15sccm and the real permeability μ’ had a high value of～200at low frequency side. In particular, a resonance frequency of4.0GHz was obtained at the Ar gas flow rate of15sccm. When the Ar gas flow rates were equal or more than12.5seem, the easy axis was perpendicular to the applied external magnetic field.(4) The FeCoAlO gradient composition thin films also showed good high frequency response when the applied external magnetic field was removed. (5) A large in-plane uniaxial magnetic anisotropy (Hk>100Oe) were obtained at Ar depositing pressure of4-12mTorr.III. FeCoAlON and FeCoZr stripe domain thin filmsThe static and dynamic properties of the FeCoAlON and FeCoZr thin films with stripe domain structure were investigated. The appearance of the stripe domain structure needs to reach a certain element content, and the film thickness must be grater than a critical value. For both kinds of the films, the multiple resonances occurred in the permeability spectra.(1) The stripe domain structure was observed in210nm thick FeCoAlON (the nitrogen partial of5%) and150nm thick FeCoZr (the Zr content of11.2at.%) thin films, it is a critical thickness for two kinds of the films, respectively.(2) For the films with stripe domain structure, the residual magnetization ratio of the in-plane hysteresis loops could reflect the angle between the orientation of magnetic moment and film plane. The smaller the residual magnetization ratio, the bigger the angle is, and the more obvious the perpendicular magnetic anisotropy is.更多还原