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首页> 外文学位 >Proprietes magnetostatiques et resonance ferromagnetique de reseaux de nanofils en configuration multicouche.
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Proprietes magnetostatiques et resonance ferromagnetique de reseaux de nanofils en configuration multicouche.

机译：多层结构纳米线阵列的静磁性能和铁磁共振。

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摘要

Arrays of multilayer nanowires have been synthesized to study their static and dynamic magnetic properties. The nanowires are columns of alternating Co94Fe5B1 and Cu layers grown in a porous alumina membrane. The objectives of this study are to control the fabrication of these arrays, to explore their magnetic properties by static and ferromagnetic resonance measurements, to develop a model which explains the behavior of the magnetic anisotropy, and to demonstrate that we can synthesize magnetically isotropic nanowire arrays.;The CoFeB/Cu multilayer nanowires are grown in a porous alumina matrix by pulsed electrodeposition. Their length is several tens of micrometers, their diameter is about 45 nm and the interwire length is around 110 nm. Two types of configuration have been studied: one consisting of a periodic CoFeB/Cu bilayer stacking, the other of CoFeB/Cu/CoFeB trilayers, separated by thick Cu layers between trilayers.;The structure of the nanowires has been characterized by scanning electrons microscopy (SEM) and by transmission electrons microscopy (TEM). These measurements showed that it is difficult to distinguish and measure the thickness of the different layers. We also observed that the CoFeB layers have a polycrystalline structure.;We present an effective anisotropy field model taking into account dipolar interactions between all the ferromagnetic layers as well as the shape anisotropy of the layers. We have generalized an existing model based on the bilayer configuration and have adapted it to the trilayer structure. A novelty of this model was to explicitly highlight the internal dipolar interaction between adjacent layers within a trilayer which makes it possible to tune the effective anisotropy of the arrays. With this model in hand we were able to study the behavior and sensitivity of the effective field to different geometric parameters of the nanowire arrays.;We then conducted static magnetic measurements with a vibrating sample magnetometer (VSM) as well as ferromagnetic resonance measurements on several bilayer and trilayer nanowire arrays. We study their qualitative behavior and we compare the experimental effective fields to those predicted by the model. This allows us to discuss the validity of the model and understand if other anisotropy contributions could have a significant effect on these materials.;Finally, we show the experimental results of VSM and ferromagnetic resonance measurements for two magnetically isotropic multilayer nanowire arrays, which are interesting from a scientific and technological point of view. The results confirm the isotropic behavior of these samples; however we do not yet understand the necessary conditions in order to obtain these types of material.;These results should open the way to a more controlled engineering of arrays of multilayer nanowires and bring a deeper understanding of what are the most relevant parameters in order to obtain specific material behaviors (in-plan or out-of-plane anisotropy, isotropy, etc.). Moreover, the model as we presented it is suitable for further improvement by, for example, taking into account additional anisotropy contributions.
机译：已经合成了多层纳米线的阵列以研究其静态和动态磁性能。纳米线是在多孔氧化铝膜中生长的交替的Co94Fe5B1和Cu层的列。这项研究的目的是控制这些阵列的制造，通过静态和铁磁共振测量来探索它们的磁性，开发一个解释磁各向异性行为的模型，并证明我们可以合成各向同性的纳米线阵列通过脉冲电沉积在多孔氧化铝基质中生长CoFeB / Cu多层纳米线。它们的长度为几十微米，直径约为45 nm，线间长度约为110 nm。研究了两种类型的配置：一种由周期性的CoFeB / Cu双层堆叠组成，另一种由三层之间的厚Cu层隔开的CoFeB / Cu / CoFeB三层组成;纳米线的结构已通过扫描电子显微镜表征（SEM）和透射电子显微镜（TEM）。这些测量表明难以区分和测量不同层的厚度。我们还观察到CoFeB层具有多晶结构。我们提出了一个有效的各向异性场模型，该模型考虑了所有铁磁层之间的偶极相互作用以及各层的形状各向异性。我们已经基于双层配置对现有模型进行了概括，并将其适应于三层结构。该模型的新颖之处在于明确强调了三层内相邻层之间的内部偶极相互作用，这使得有可能调节阵列的有效各向异性。有了这个模型，我们就能够研究有效场对纳米线阵列不同几何参数的行为和敏感性。然后，我们使用振动样本磁力计（VSM）进行了静态磁测量以及在多个磁铁上进行了铁磁谐振测量双层和三层纳米线阵列。我们研究了它们的定性行为，并将实验有效场与模型预测的场进行了比较。这使我们能够讨论模型的有效性，并了解其他各向异性的贡献是否会对这些材料产生显着影响。最后，我们展示了两个磁各向同性的多层纳米线阵列的VSM和铁磁共振测量的实验结果，这很有趣从科学技术的角度来看。结果证实了这些样品的各向同性行为。然而，我们尚不了解获得这些类型材料的必要条件。这些结果应为更受控地设计多层纳米线阵列开辟道路，并加深对最相关参数的理解，以便获得特定的材料行为（平面内或平面外各向异性，各向同性等）。此外，我们提出的模型适合进一步改进，例如，考虑到其他各向异性的影响。

著录项

  • 作者

    Hadj-Messaoud, Salah.;

  • 作者单位

    Ecole Polytechnique, Montreal (Canada).;

  • 授予单位 Ecole Polytechnique, Montreal (Canada).;
  • 学科 Physics Electricity and Magnetism.;Physics Condensed Matter.;Engineering Materials Science.
  • 学位 M.Sc.A.
  • 年度 2012
  • 页码 136 p.
  • 总页数 136
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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