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Exchange coupling at cobalt/nickel oxide interfaces.

机译：钴/氧化镍界面的交换耦合。

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摘要

Spin arrangement at interfaces in layered magnetic materials is of vital importance to the emerging field of spintronics. Knowledge of how and why the interfacial spins behave in a certain way will aid in the development of future magnetic-based memories.;Much exploration has taken place in the interlayer exchange coupling (IEC) of ferromagnetic heterostructures with in-plane anisotropy. Only recently has it become apparent that to achieve the goals of increased areal density in magnetic memory a push for exploring magnetic materials with perpendicular magnetic anisotropy (PMA) must occur. An interesting and promising candidate for such a magnetic system is [Co/Pt]/NiO/[Co/Pt], where two [Co/Pt] multilayers with PMA are separated by a thin, insulating, antiferromagnetic NiO layer and display oscillatory coupling with NiO thickness. This magnetic heterostructure displays an entirely new IEC where the Ni spins within the NiO layer cant in concert with the adjacent [Co/Pt] layers, causing the periodicity of the oscillatory coupling to coincide with the NiO antiferromagnetic ordering parameter. The strength and sign of this coupling, either positive (favoring parallel alignment) or negative (favoring anti-parallel alignment), can be tuned with slight changes in the NiO layer thickness. The origin of the oscillatory IEC was investigated using advanced microscopy and spectroscopy techniques.;For antiferromagnetically coupled [Co/Pt] layers, the competition between magnetostatic coupling and IEC gives rise to a region of overlapping domains (resulting in a ferromagnetically coupled stripe). Discovered with high resolution magnetic force microscopy and quantitatively modeled with micromagnetic simulation, the width of this overlap region scales inversely with the IEC.;Heterostructures of Co/NiO/[Co/Pt], where the Co ([Co/Pt]) has in-plane (out-of-plane) anisotropy, allow for isothermal tuning of the hysteresis loop shift along the applied field axis at room temperature, as well as display a greatly enhanced blocking temperature (increase of more than 175K). The presence of the [Co/Pt] multilayer with PMA is responsible for the enhancement. In addition, these structures display temperature dependent exchange bias training effects, which have been successfully modeled using a phenomenological thermodynamic approach.
机译：分层磁性材料中界面处的自旋排列对于自旋电子学的新兴领域至关重要。了解界面自旋如何以及为什么以某种方式发生行为，将有助于未来基于磁性的存储器的发展。在具有平面内各向异性的铁磁异质结构的层间交换耦合（IEC）方面已经进行了很多探索。直到最近才变得明显，为了实现增加磁存储器中的面密度的目标，必须进行探索具有垂直磁各向异性（PMA）的磁性材料的推动。这种磁系统的一个有趣且有希望的候选者是[Co / Pt] / NiO / [Co / Pt]，其中带有PMA的两个[Co / Pt]多层由薄的绝缘反铁磁NiO层隔开并显示出振荡耦合NiO厚度。这种磁性异质结构显示了一个全新的IEC，其中Ni在NiO层内与相邻的[Co / Pt]层一起自旋，从而导致振荡耦合的周期与NiO反铁磁有序参数一致。可以通过改变NiO层的厚度来调整这种耦合的强度和符号，无论是正向（有利于平行排列）还是负向（有利于反平行排列）。使用先进的显微镜和光谱技术研究了振荡IEC的起源。对于反铁磁耦合的[Co / Pt]层，静磁耦合和IEC之间的竞争产生了一个相互重叠的区域（导致铁磁耦合条带化）。通过高分辨率磁力显微镜发现并通过微磁模拟进行定量建模，该重叠区域的宽度与IEC成反比。平面内（平面外）各向异性，可在室温下对沿施加的场轴的磁滞回线位移进行等温调整，并显示出大大提高的阻挡温度（增加超过175K）。具有PMA的[Co / Pt]多层膜的存在是增强的原因。此外，这些结构还显示出依赖温度的交换偏差训练效果，这些效果已使用现象学热力学方法成功建模。

著录项

  • 作者

    Baruth, Andrew Gerald.;

  • 作者单位

    The University of Nebraska - Lincoln.;

  • 授予单位 The University of Nebraska - Lincoln.;
  • 学科 Physics Electricity and Magnetism.;Physics Condensed Matter.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 239 p.
  • 总页数 239
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 电磁学、电动力学;工程材料学;
  • 关键词

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