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Exchange bias training effect in magnetically coupled bilayers.

机译：磁性耦合双层中的交换偏压训练效果。

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摘要

Interfaces in magnetically coupled bilayer heterostructures play a vital role in novel spintronics devices. Particularly, control of the interface spin structure enables the development of progressively down-scalable magnetic read-heads which are of major importance for non volatile magnetic recording media. Exchange bias and its accompanying training effect are fundamental magnetic coupling phenomena taking place at the interfaces of antiferromagnetic/ferromagnetic and hard/soft ferromagnetic bilayers.;Here, in my thesis I present the experimental results of exchange bias training in the prototypical antiferromagnetic/ferromagnetic exchange bias system CoO/Co and the corresponding coupling and aging phenomena in the all ferromagnetic hard/soft bilayer CoPtCrB/CoCr. The latter system provides experimental access to its pinning layer magnetization thereby allowing to measure fundamental properties of exchange bias and its corresponding training phenomenon. A phenomenological theory is best fitted to all experimental training data of antiferromagnetic/ferromagnetic and hard/soft ferromagnetic bilayers evidencing the universality of the theory. My studies are further extended to the temperature dependence of the exchange bias training effect. Again, excellent agreement between experiment and theory confirms the remarkable universality of the underlying phenomenological approach. Furthermore, the dependence of the exchange bias training on the ferromagnetic film thickness is investigated in a CoO/Co-wedge sample. Scaling behavior with collapse of the temperature and thickness dependent parameters onto a single master curve is presented. Magnetotransport measurements are used for complementary studies of exchange bias in CoO/Co-heterostructures. Here, exchange bias produces a shift of the magnetoresistance curve along the magnetic field axis and an additional asymmetry along the resistance axis. The dynamic non-equilibrium properties of the exchange bias training effect are investigated via the sweep rate dependence of the exchange bias field. A dynamical enhancement of the exchange bias training effect has been observed in both CoO/Co and CoPtCrB/CoCr bilayers with increasing sweep rate of the applied magnetic field. A generalized theory has been developed for the dynamical enhancement studies confirming once more the consistency and universality of the phenomenological approach.
机译：磁耦合双层异质结构中的界面在新型自旋电子器件中起着至关重要的作用。特别地，对界面自旋结构的控制使得能够开发可逐步缩小尺寸的磁读取头，这对于非易失性磁记录介质而言至关重要。交换偏置及其伴随的训练效果是在反铁磁/铁磁和硬/软铁磁双层界面上发生的基本磁耦合现象。；在本文中，我介绍了在典型的反铁磁/铁磁交换中进行交换偏置训练的实验结果。偏置系统CoO / Co以及所有铁磁硬/软双层CoPtCrB / CoCr中的相应耦合和老化现象。后者系统提供了对其钉扎层磁化强度的实验访问，从而允许测量交换偏压的基本属性及其相应的训练现象。现象学理论最适合反铁磁/铁磁双层和硬/软铁磁双层的所有实验训练数据，证明了该理论的普遍性。我的研究进一步扩展到交换偏差训练效果的温度依赖性。同样，实验与理论之间的出色一致性证实了潜在现象学方法的非凡普遍性。此外，在CoO / Co-wedge样品中研究了交换偏置训练对铁磁膜厚度的依赖性。给出了随温度和厚度相关的参数崩溃到单个主曲线上的缩放行为。磁传输测量用于CoO / Co-异质结构中交换偏压的补充研究。在此，交换偏压导致磁阻曲线沿磁场轴移动，并导致沿电阻轴产生额外的不对称性。通过交换偏置场的扫描速率依赖性，研究了交换偏置训练效果的动态非平衡特性。随着施加磁场扫描速率的增加，在CoO / Co和CoPtCrB / CoCr双层膜中都观察到了交换偏压训练效果的动态增强。已经为动力增强研究开发了一种通用理论，再次证实了现象学方法的一致性和普遍性。

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  • 作者

    Polisetty, Srinivas.;

  • 作者单位

    The University of Nebraska - Lincoln.;

  • 授予单位 The University of Nebraska - Lincoln.;
  • 学科 Nanoscience.;Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 236 p.
  • 总页数 236
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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