Magnetic Correlations and Quantum Critical Points

这是一个实验凝聚态物理项目，将研究几种稀土和锕系金属间化合物中新颖的T=0磁相变。这些材料中的磁相变发生在任何实验可及的温度或能量尺度下，因此磁相关的时间和长度尺度以一种不寻常的方式耦合在一起。本研究将以整体的方式调查这些相关性。它们的时间衰减将通过非弹性中子散射、交流磁化率和磁化时间依赖性的直接测量来研究。测量的目的是确定温度-成分图或温度-压力相图中磁相关性自由发展的区域，以及无序或其他内在影响相关性尺度的区域。通过比较那些无序程度很小或很严重的系统，以及那些无序涉及矩稀释或在磁矩的化学环境中无序的系统，将为这些不寻常的磁铁的真正临界状态的扩展制定一个微观标准。在Ce1-xLaxRu2Si2， U1-xThxPdxAl3中，矩无序的影响将被研究，而在CeRu2(Si1-xGex)2和Ce(Ru1-xTx)2Si2, （T=Fe或Ni）中，配体无序是不同的。这个实验凝聚态物理项目研究了结构复杂的稀土和锕系金属间化合物中不寻常的磁性行为。这些材料中的磁体被认为只有在绝对零度时才有秩序，这在实验上是无法得到的。作为一种替代方法，通过研究磁性在温度区间内的波动，直至最低温度，来寻求有关磁性行为的信息。对磁性波动行为的分析揭示了化合物中原子矩运动相互关联的机制。相关关系还反映了晶格中缺陷和化学无序的影响。所有这些效应必须被整理出来，以得到这些材料的基本磁性。从基础和技术的角度来看，结果都很有趣。这项研究为最先进的实验方法提供了极好的训练。负责这个项目的女教授因其教育贡献而闻名。

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.