Neutron Scattering Studies of Solids with Strong Fluctuations

该项目探索具有强烈磁学、电子学或结构性质起伏的固体的动力学性质。我们将通过磁中子散射来研究自旋系统中的杂质束缚态。这些实验使用杂质来揭示宿主中的局域动力学关联，并将促进我们对强起伏系统中杂质的理解。横向晶格振动会导致固体随着温度的升高而收缩。负热膨胀材料中的晶格动力学将通过非弹性中子束散射来研究。磁体中受挫的相互作用可以抑制有序化，并产生具有很强局域约束的涨落相。中子散射将被用来建立晶体模型系统中的自旋哈密顿量，并提供关于动态关联的详细信息。将进行实验来研究金属中的强烈磁涨落。这些实验将探索反铁磁重费米子系统中从自旋波到电子空穴对激发的交叉，并探索几何受挫在这些系统中的作用。该项目的教育目标是培养人们对中子散射技术的认识，培养出创新和有能力的实验者和物理学家，他们可以为未来十年美国最大的科学项目：散裂中子源做出贡献并加以利用。尽管固体在宏观长度尺度上看起来是静态的，但它们在纳米尺度上是动态的。理解这种运动很重要，尤其是在技术向更小维度推进的情况下。这个项目使用非弹性中子散射来研究固体在纳米尺度和皮秒尺度上的涨落。重点放在涨落在某些具有磁性原子的材料中起重要作用的材料上，量子涨落完全抑制了任何宏观的磁响应。然而，杂质可以在这些系统中诱导磁性，就像杂质增加半导体的导电性一样。将进行实验以了解这些系统中接近杂质的磁性。随着原子运动幅度的增加，大多数固体在受热时膨胀。然而，在某些材料中，原子运动导致收缩。将进行实验，以确定哪种类型的原子运动会导致收缩，竞争相互作用会导致磁铁的强烈波动。人们对这些波动的磁铁知之甚少，将通过磁中子散射进行检查。最后，将进行实验，以探测导致异常金属性质和超导电性的金属中的磁性波动。该项目的教育目标是提高人们对中子散射技术的认识，培养出能够为这个未来十年美国最大的科学项目做出贡献并发挥作用的创新和有能力的科学家。散裂中子源。

This project explores dynamical properties of solids with strong fluctuations of their magnetic, electronic or structural properties. Impurity bound states in spin systems will be examined through magnetic neutron scattering. The experiments use impurities to reveal local dynamic correlations in the host and will also advance our understand of impurities in strongly fluctuating systems. Transverse lattice vibrations can cause solids to contract with increasing temperature. Lattice dynamics in materials with negative thermal expansion will be examined through inelastic neu-tron scattering. Frustrated interactions in magnets can suppress ordering and give rise to fluctuating phases with strong local constraints. Neutron scattering will be used to establish the spin Hamiltonian in crystalline model systems and provide detailed information about dynamic correlations. Experiments will be performed to examine strong magnetic fluctuations in metals. The experiments will probe the crossover from spin wave to electron hole pair excitations in anti-ferromagnetically ordered heavy fermion systems and explore the role of geometrical frustration in these systems. The educational goal of the project is to create awareness of the neutron scattering technique and produce innovative and competent experimentalists physicists that can contribute to and take advantage of the nations largest scientific project in the next decade: The Spallation Neutron Source.%%%While solids appear static on macroscopic length scales, they are dynamic on the nanometer scale. Understanding such motion is important, especially as technology pushes to smaller dimensions. This project examines fluctuations in solids on the nanometer length scale and pico second time scale using inelastic neutron scattering. The focus is on materials where fluctuations play an important role In certain materials with magnetic atoms, quan-tum fluctuations completely suppress any macroscopic magnetic response. Impurities can however induce magnetism in these systems just as impurities increase the electric conduc-tivity of semiconductors. Experiments will be carried out to understand magnetism close to impurities in these systems. Most solids expand on heating as the amplitude of atomic motion increases. However in some materials, atomic motion leads to contracti6n. Experiments will be carried out to determine what type of atomic motion leads to contraction Competing interactions can lead to strong fluctuations in magnets. These fluctuating magnets are poorly understood and will be examined through magnetic neutron scattering. Finally experiments will be carried out to probe magnetic fluctuations in metals that lead to anomalous metallic properties and superconductivity. The educational goal of the project is to create awareness about the neutron scattering technique and produce innovative and competent scientists that can contribute to and take advantage of the nations largest scientific project in the next decade. The Spallation Neutron Source.