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首页> 外文学位 >Perpendicular exchange bias in ferromagnetic/antiferromagnetic multilayers and magnetization switching.
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Perpendicular exchange bias in ferromagnetic/antiferromagnetic multilayers and magnetization switching.

机译：铁磁/反铁磁多层中的垂直交换偏压和磁化强度转换。

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摘要

Exchange bias is an important magnetic interaction existing at the interface between ferromagnetic (FM) and antiferrromagnetic (AFM) coupled layers. This phenomenon has attracted an extensive amount of attention due to its technological applications and rich physics. Better understanding of the exchange bias and related magnetic behaviors of artificial magnetic structures will have significant impact on improving device performances and gaining insight into fundamental magnetic physics.;Previous studies on exchange bias have been focused on applying the cooling field along the sample easy axis, and most of the angular dependent magnetization reversal studies of thin film structures are limited in plane without consideration of shape anisotropy. In this dissertation, we focus on our research of establishment of perpendicular exchange bias through the control of cooling field direction. Investigation of temperature and constituent layer thickness effects demonstrates that the exchange bias induced by perpendicular field cooling has very similar behaviors to the conventional longitudinal exchange bias. Although the magnitudes of the induced anisotropies have quantitative differences for the two field cooling geometries, the perpendicular exchange bias still reflects the same interfacial nature of the FM/AFM interaction. In our research, systematic angular dependent magnetization reversal measurements have been performed for both perpendicular and longitudinal exchange biases. Angular dependent hysteresis loops with distinctive characteristics from convention have been observed for out-of-plane measurements. To explain the magnetization reversal process and quantify the observed angular dependence, a three-dimensional magnetization reversal model based on S-W coherent rotation hypothesis has been developed. After taking into account the competitive field cooling induced anisotropies and the thin film shape anisotropy, the three-dimensional coherent rotation model alone can quantitatively explain the observed out-of-plane angular dependence for both field cooling geometries. Magnetization reversal is found to be accomplished by coherent rotation out of the plane determined by anisotropic axis and applied field. The model is also applicable in predicting the more general thin-film magnetization reversal with out-of-plane applied fields.;Our study provides direct evidence that through appropriate field cool procedure exchange bias can be established and controlled in any directions in the space. The realization of exchange bias in conventional soft FM thin films indicates that perpendicular anisotropy can be cost-effectively achieved instead of using high cost perpendicular films for recording and sensor applications.
机译：交换偏压是在铁磁（FM）和反铁磁（AFM）耦合层之间的界面处存在的重要磁性相互作用。由于其技术应用和丰富的物理特性，这种现象已经引起了广泛的关注。更好地了解人造磁性结构的交换偏置和相关的磁性行为将对改善器件性能和深入了解基本的磁性物理学产生重大影响。；以前对交换偏置的研究一直集中在沿样品易轴方向施加冷却场，薄膜结构的大多数与角度相关的磁化反转研究都在平面内受到限制，而没有考虑形状各向异性。本文主要研究通过控制冷却场方向建立垂直交换偏压的研究。对温度和组成层厚度影响的研究表明，垂直场冷却引起的交换偏压具有与常规纵向交换偏压非常相似的行为。尽管对于两个场冷却几何形状，各向异性的大小存在定量差异，但垂直交换偏压仍反映了FM / AFM相互作用的相同界面性质。在我们的研究中，已经针对垂直和纵向交换偏置进行了系统的角度相关的磁化反转测量。对于平面外测量，已观察到具有与众不同的常规特性的角度依赖性磁滞回线。为了解释磁化反转过程并量化观测到的角度依赖性，已开发了基于S-W相干旋转假设的三维磁化反转模型。在考虑了竞争性的场冷却引起的各向异性和薄膜形状各向异性之后，仅三维相干旋转模型就可以定量解释两种场冷却几何形状所观察到的面外角度依赖性。发现磁化反转是通过相干旋转出各向异性轴和外加磁场确定的平面来完成的。该模型还可用于预测平面外施加磁场时更普遍的薄膜磁化反转。我们的研究提供了直接的证据，表明通过适当的磁场冷却程序，可以在空间的任何方向上建立和控制交换偏置。常规软FM薄膜中交换偏置的实现表明，可以垂直有效地实现垂直各向异性，而不是将高成本垂直膜用于记录和传感器应用。

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  • 作者

    Xing, Hao.;

  • 作者单位

    University of Houston.;

  • 授予单位 University of Houston.;
  • 学科 Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 122 p.
  • 总页数 122
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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