Magnetic Correlations and Quantum Critical Points

9977300Aronson这是一个实验凝聚态物理项目，将研究几种稀土和金属间化合物中新颖的T=0磁性相变。这些材料的磁相变发生在任何实验可获得的温度或能量范围以下，因此磁关联的时间和长度尺度以一种不寻常的方式耦合在一起。这项研究将以一种整体的方式调查这些相关性。我们将使用非弹性中子散射、交流磁化率和磁化强度随时间变化的直接测量来研究它们的时间衰减。测量的目的是确定温度-组成或温度-压力相图上磁关联自由发展的区域，以及无序或其他内在影响关联标度的区域。通过比较无序度很小或很深的系统，以及在磁矩的化学环境中无序涉及瞬间稀释或无序的系统，将发展出一种微观标准，以扩展这些不寻常磁体的真正临界区域。我们将研究Ce1-xLaxRu2Si2，U1-xThxPdxAl3的磁矩无序效应，而CeRu2(Si1-xGex)2和Ce(Ru1-xTx)2Si2(T=Fe或Ni)中的配位无序是不同的。这些材料中的磁体被认为只能在绝对零度下排序，而绝对零度是无法通过实验获得的。作为另一种选择，通过研究直到可用最低温度的温度区间内磁性质的波动来寻找关于磁行为的信息。对波动磁性行为的分析揭示了倾向于将化合物中原子矩的运动关联起来的机制。关联还反映了晶格中缺陷和化学无序的影响。必须对所有这些效应进行分类，才能得到这些材料的基本磁性。从基本和技术角度来看，这些结果都是有意义的。这项研究提供了最先进的实验方法的优秀培训。负责这个项目的女教授以她的教育贡献而闻名。

9977300AronsonThis is an experimental condensed matter physics project that will investigate the novel T=0 magnetic phase transitions in several rare earth and actinide intermetallic compounds. The magnetic phase transition in these materials occurs below any experimentally accessible temperature or energy scale so the time and length scales of magnetic correlations are coupled in an unusual way. The research will investigate these correlations in an integral fashion. Their time decay will be studied using inelastic neutron scattering, AC susceptibility, and direct measurements of the time dependence of the magnetization. The objective of the measurements is to identify the region of the temperature-composition or temperature-pressure phase diagram on which magnetic correlations develop freely, and regions in which disorder or other intrinsic effects the scale for correlations. By comparing systems in which disorder is minimal or profound, and those in which the disorder involves moment dilution or disorder n the chemical environments of the magnetic moments, a microscopic criterion will be developed fot he extend of the truly critical regime of these unusual magnets. The effects of moment disorder will be studied in Ce1-xLaxRu2Si2, U1-xThxPdxAl3, while ligand disorder is varied in CeRu2(Si1-xGex)2 and Ce(Ru1-xTx)2Si2, (T=Fe or Ni).%%%This experimental condensed matter physics project investigates the unusual magnetic behavior in structurally complex rare earth and actinide intermetallic compounds. The magnets in these materials are thought to order only at absolute zero, which is not experimentally obtainable. As an alternative, information about the magnetic behavior is sought by studying the fluctuations in the magnetic properties over temperature intervals down to the lowest temperatures available. An analysis of the fluctuating magnetic behavior sheds light on the mechanisms tending to correlate the motions of the atomic moments in the compounds. The correlations also reflect the influence of defects and chemical disorder in the crystal lattices. All these effects must be sorted out to get to the fundamental magnetism in these materials. The results are of interest from both fundamental and technical viewpoints. The research provides excellent training in the state of the art experimental methods. The female professor in charge of this project is noted for her educational contributions.