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Magnetic anisotropy graded media and iron-platinum alloy thin films.

机译：磁各向异性梯度介质和铁铂合金薄膜。

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摘要

Anisotropy graded media are promising to overcome the writability problem in achieving ultrahigh areal density for magnetic recording media. To more conveniently study and compare various media with regard to a particular figure of merit, a new energy landscape method of analysis is suggested. Using this method, the theoretical limit of the figure of merit for a graded medium is found to be 4. This limit can be approached by a graded medium with anisotropy quadratically increasing from zero to its maximum value. In order to characterize the anisotropy distribution of a graded medium, hard axis loops of graded media with various anisotropy profiles are simulated and analyzed. It is found that the second derivative of the hard axis loop can give useful information on the anisotropy distribution in a graded medium. Fe50Pt 50 with the L10 structure, as one of the magnetically hardest materials, has great potential for media application. By using a first-principles calculation method, the magnetic and electronic structures of L10 structured Fe50Pt50 have been studied. These calculations show that although the ferromagnetic phase is the most stable phase for Fe 50Fe50 with the L10 structure, there is a competition between the antiferromagnetic and the ferromagnetic phases when the ratio of lattice constants, c/a, decreases. Experimental investigations of Fe 50Pt50 films with graded order parameter fabricated by varying the growth temperature during deposition demonstrate that these films have much smaller switching field than fully ordered Fe50Pt50, which suggests it is possible to make graded media by using this kind of films. Fe100-xPtx films with compositional gradient were also studied; however, the large easy axis dispersion in these films makes them unsuitable for the fabrication of graded media. Films with [FePt3(ordered)/FePt 3(disordered)]n superlattices were deposited on MgO substrates and sapphire substrates. It was found that the superlattices deposited on MgO substrates show higher exchange bias field. Polarized neutron reflectivity results show that ferromagnetic layers on MgO substrates contain more antiferromagnetic component than those on sapphire substrates. The larger exchange bias of the superlattice on MgO substrate is hypothesized to be due to larger exchange bias in its ferromagnetic layers.
机译：各向异性梯度介质有望克服磁记录介质实现超高面密度的可写性问题。为了更方便地研究和比较各种介质的特定品质因数，提出了一种新的能源格局分析方法。使用此方法，发现渐变介质的品质因数的理论极限为4。各向异性可以从零到其最大值呈二次方递增的渐变介质来逼近此极限。为了表征梯度介质的各向异性分布，对具有各种各向异性特征的梯度介质的硬轴环进行了模拟和分析。发现硬轴环的二阶导数可以提供有关渐变介质中各向异性分布的有用信息。具有L10结构的Fe50Pt 50是最难磁化的材料之一，在媒体应用方面具有巨大潜力。通过第一性原理计算方法，研究了L10结构的Fe50Pt50的磁性和电子结构。这些计算表明，尽管对于具有L10结构的Fe 50Fe50，铁磁性相是最稳定的相，但是当晶格常数c / a的比率减小时，反铁磁性相和铁磁性相之间就会发生竞争。通过改变沉积过程中的生长温度制备的具有梯度级参数的Fe 50Pt50膜的实验研究表明，这些膜的开关场远小于完全有序的Fe50Pt50，这表明可以通过使用这种膜来制备梯度介质。还研究了具有梯度成分的Fe100-xPtx薄膜；但是，这些薄膜中的大易轴分散性使其不适用于渐变介质的制造。具有[FePt3（有序）/ FePt 3（无序）] n超晶格的薄膜沉积在MgO衬底和蓝宝石衬底上。发现沉积在MgO衬底上的超晶格显示出较高的交换偏压场。极化中子反射率结果表明，MgO衬底上的铁磁层比蓝宝石衬底上的铁磁层包含更多的反铁磁成分。据推测，MgO衬底上超晶格的较大交换偏压是由于其铁磁层中较大的交换偏压所致。

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  • 作者

    Lu, Zhihong.;

  • 作者单位

    The University of Alabama.;

  • 授予单位 The University of Alabama.;
  • 学科 Physics Condensed Matter.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 184 p.
  • 总页数 184
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 工程材料学;
  • 关键词

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