• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文学位 >A tin-119 and gadolinium-155 Moessbauer spectroscopy and neutron diffraction study of R3T4X4 (R = rare-earth, T = copper, silver, X = tin, germanium) compounds.
【24h】

A tin-119 and gadolinium-155 Moessbauer spectroscopy and neutron diffraction study of R3T4X4 (R = rare-earth, T = copper, silver, X = tin, germanium) compounds.

机译：R3T4X4（R =稀土，T =铜，银，X =锡，锗）化合物的锡119和ado 155的Moessbauer光谱和中子衍射研究。

获取原文
获取原文并翻译 | 示例
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The isostructural R3T4X4 (R: rare earth, T:Mn,Pd,Cu,Ag, X:Si,Ge,Sn) family of compounds have been extensively studied recently due to the rich variety of magnetic behaviour exhibited: the two rare earth sublattices often order with quite different moment values and distinct magnetic structures. In some cases the rare earth sites will also have quite different ordering temperatures. Several of the series, R 3Cu4Sn4 and R3Ag4Sn 4 and R3Cu4Ge4, appear not to follow the expected de Gennes scaling law of transition temperatures despite the structural uniformity of the system. Moreover, the system suffers from a common problem in rare earth intermetallic systems: an important lack of data and understanding of the Sm and Gd members.;We find that a simple isotropic hyperfine field transfer model successfully describes the 119Sn Mössbauer spectra of several R 3T4Sn4 (T:Cu,Ag) compounds. 119Sn Mössbauer spectroscopy also reveals important magnetic interactions previously missed: Nd3Cu4Sn4 data exhibits a clear magnetic contribution at temperatures at which neutron diffraction data did not, while Ho3Cu4Sn4 exhibited magnetic interactions above the ordering temperature determined by neutron diffraction. The Sm 3Ag4Sn4 and Sm3Cu4Sn 4 compounds proved to behave entirely differently than previously thought: the former undergoes magnetic ordering at 26K rather than 9K, and shows evidence of anisotropic field transfer, while Sm3Cu4Sn4 fails to order and instead exhibits slow moment dynamics. The Gd compounds also yield surprising results as Gd3Cu4Ge4 and Gd3Ag4Sn4 order at far higher temperature than previously thought, while Gd3Cu4Sn4 exhibits the most complex 119Sn Mössbauer spectrum due only to the moments at the Gd-2d site.;The R3T4X4 system remains highly magnetically complex and diverse, however the magnetic landscape has been significantly altered. The flat plate mounting technique for neutron diffraction, especially when combined with Mössbauer spectroscopy data, allows for the determination of the magnetic structures of Sm3Ag4Sn4 as well as Gd3Ag4Sn4 and partially of Gd 3Cu4Sn4, showing great promise as an important new experimental tool.;Capitalizing on the presence of Sn in many of these compounds, we have used 119Sn Mössbauer spectroscopy as a probe of local magnetism at the Sn sites in the structure. Although Sn carries no magnetic moment, a transferred field from the rare earth neighbours is observed, as both Sn sites in the structure have nearest neighbours from both rare earth sublattices. We also performed 155Gd Mössbauer spectroscopy on three Gd compounds, probing the local magnetism at the 155Gd nuclei directly. Using the newly developed flat plate mounting for highly absorbing samples, we performed neutron diffraction on several Sm and Gd compounds to probe the long range spatial symmetry of the rare earth magnetic moments. The Mössbauer spectroscopy and neutron scattering results were then combined as verification of consistency, but more importantly as complementary sources of magnetic information allowing us to draw conclusions that otherwise could not be drawn with either of the experimental techniques alone.
机译：由于显示出丰富的磁行为，最近对同构结构的R3T4X4（R：稀土，T：Mn，Pd，Cu，Ag，X：Si，Ge，Sn）族进行了广泛的研究：两个稀土亚晶格通常订购时的力矩值和磁结构明显不同。在某些情况下，稀土站点的订购温度也将完全不同。尽管系统结构均匀，但其中一些序列R 3Cu4Sn4和R3Ag4Sn 4和R3Cu4Ge4似乎未遵循预期的过渡温度的de Gennes定标定律。此外，该系统还存在稀土金属间体系中的一个普遍问题：数据的缺乏和对Sm和Gd成员的了解。我们发现一个简单的各向同性超精细场传输模型成功地描述了多个R 3T4Sn4的119SnMössbauer光谱（T：Cu，Ag）化合物。 119SnMössbauer光谱还显示了以前错过的重要磁相互作用：Nd3Cu4Sn4数据在中子衍射数据没有的温度下表现出明显的磁作用，而Ho3Cu4Sn4在高于中子衍射确定的有序温度下表现出磁相互作用。 Sm 3Ag4Sn4和Sm3Cu4Sn 4化合物的行为与以前认为的完全不同：前者在26K而不是9K时经历了磁有序化，并显示出各向异性的场转移证据，而Sm3Cu4Sn4则没有有序化，而是表现出慢矩动力学。 Gd化合物还产生令人惊讶的结果，因为Gd3Cu4Ge4和Gd3Ag4Sn4在比以前认为的温度高得多的温度下有序排列，而Gd3Cu4Sn4表现出最复杂的119SnMössbauer光谱，仅是由于在Gd-2d处的瞬间。多样性，但是磁性环境已经发生了显着变化。用于中子衍射的平板安装技术，特别是与Mössbauer光谱数据结合使用时，可以确定Sm3Ag4Sn4，Gd3Ag4Sn4以及部分Gd 3Cu4Sn4的磁性结构，显示出作为重要的新实验工具的广阔前景。在许多此类化合物中存在Sn的情况下，我们已使用119SnMössbauer光谱作为结构中Sn处的局部磁性探针。尽管Sn没有磁矩，但是观察到了来自稀土邻域的转移磁场，因为结构中的两个Sn位置都距离两个稀土亚晶格最近。我们还对三种Gd化合物进行了155GdMössbauer光谱分析，直接探测了155Gd原子核的局部磁性。使用新开发的用于高吸收样品的平板安装架，我们对几种Sm和Gd化合物进行了中子衍射，以探测稀土磁矩的长距离空间对称性。然后将Mössbauer光谱学和中子散射结果结合起来，作为一致性的验证，但更重要的是，作为磁信息的补充源，这使我们能够得出结论，而使用任何一种实验技术都无法得出结论。

著录项

  • 作者

    Voyer, Christian.;

  • 作者单位

    McGill University (Canada).;

  • 授予单位 McGill University (Canada).;
  • 学科 Physics Condensed Matter.
  • 学位 Ph.D.
  • 年度 2011
  • 页码 191 p.
  • 总页数 191
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号