Magnetic Correlations and Quantum Critical Points

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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.