Exotic Magnetic Behavior of Pure and Doped Spin-Gap / Spin-Liquid Systems Studied by Muon Spin Relaxation

这个实验研究项目致力于研究纯自旋间隙系统和掺杂自旋间隙系统以及自旋液体系统中由μ子自旋弛豫研究的异常磁行为。主要的兴趣是低维和/或几何受挫的自旋系统。我们感兴趣的是自旋冻结形成/缺失的条件，挫折的作用，电荷掺杂和磁稀释的影响。更详细地说，四个感兴趣的主题和系统是：1)准一维之形自旋链SrCuO2和LixV2O5的有序温度和/或有序矩大小问题；2) Sr2(Cu,Zn)4O6, LaCuO2.5和（Ca,Mg）（V,Ti）2O5的电荷/空位掺杂效应；3)纯和扰动几何受挫体系LiV2O4， （Y,Sc）Mn2， CePt2Sn2的基态；(4) La,Sr,Ca)14Cu24O41中线性链和双支梯的磁性。在TRIUMF进行了介子自旋弛豫实验，在哥伦比亚大学进行了磁化率测量，在JAERI进行了中子散射研究。该研究项目本质上是跨学科的，涉及一名或多名研究生或研究生，他们接受了优秀的培训，为工业、政府实验室或学术界的职业生涯做准备。这个实验基础研究项目致力于研究各种无机化合物晶体样品的异常磁性行为。感兴趣的问题是样品中磁性物质的局部行为，并在这项工作中使用了一种称为“μ子自旋弛豫”的先进实验方法。测量必须在一个特殊的加速器设施中进行，在那里产生μ子（μ介子）并注入感兴趣的样品中。测量揭示了样品内部那些位置的磁场强度，通常是在内部磁矩附近，在那里介子在衰变之前被捕获。我们感兴趣的是自旋冻结形成/缺失的条件，挫折的作用，电荷掺杂和磁稀释的影响。更详细地说，四个感兴趣的主题和系统是：1)准一维之字型自旋链SrCuO2和LixV2O5的有序温度和/或有序矩大小问题；2) Sr2(Cu,Zn)4O6, LaCuO2.5和（Ca,Mg）（V,Ti）2O5的电荷/空位掺杂效应；3)纯和扰动几何受挫体系LiV2O4， （Y,Sc）Mn2， CePt2Sn2的基态；(4) La,Sr,Ca)14Cu24O41中线性链和双支梯的磁性。在TRIUMF进行了介子自旋弛豫实验，在哥伦比亚大学进行了磁化率测量，在JAERI进行了中子散射研究。这项研究的结果将在磁学和物理理论中具有重要意义。它们可能会导致应用于化学和纳米级电子器件的新方法。该研究项目本质上是跨学科的，涉及一名或多名研究生或研究生，他们接受了优秀的培训，为工业、政府实验室或学术界的职业生涯做准备。＊＊＊

w:\awards\awards96\*.doc 9802000 Uemura This experimental research project is devoted to unusual magnetic behavior in pure and doped spin-gap systems, and in spin-liquid systems, as studied by muon spin relaxation. Of principal interest are low-dimensional and/or geometrically frustrated spin systems. Of interest are conditions for the formation/absence of spin freezing, the role of frustration, and effects of charge doping and magnetic dilution. In more detail, four topics and systems of interest are: 1) questions of ordering temperature and/or ordered moment size in quasi 1-d zig-zag spin chain SrCuO2 and LixV2O5; 2) charge/vacancy doping effects in 2-leg ladders Sr2(Cu,Zn)4O6, LaCuO2.5, and (Ca,Mg)(V,Ti)2O5; 3) ground state of pure and perturbed geometrically frustrated systems LiV2O4, (Y,Sc)Mn2, CePt2Sn2; and 4) magnetic properties of linear chains and 2-leg ladders in the hybrid (La,Sr,Ca)14Cu24O41. The muon spin relaxation experiments are performed at TRIUMF, magnetic susceptibility measurements at Columbia and neutron scattering studies at JAERI. This research program is interdisciplinary in nature and involves one or more graduate or postgraduate students, who receive excellent training in preparation for careers in industry, government laboratories or academia. %%% This experimental basic research project is devoted to unusual magnetic behavior in crystalline specimens of a variety of inorganic chemical compounds. The questions of interest are the local behavior of the magnetic species in the samples, and an advanced experimental method called "muon spin relaxation" is used in this work. The measurement has to be made at a special accelerator facility where the muons (mu mesons), are produced and injected into the sample of interest. The measurement reveals the magnetic field strength inside the sample at those loca tions, often near internal magnetic moments, where the muons become trapped before they undergo decay. Of interest are conditions for the formation/absence of spin freezing, the role of frustration, and effects of charge doping and magnetic dilution. In more detail, four topics and systems of interest are: 1) questions of ordering temperature and/or ordered moment size in quasi 1-d zig- zag spin chain SrCuO2 and LixV2O5; 2) charge/vacancy doping effects in 2-leg ladders Sr2(Cu,Zn)4O6, LaCuO2.5, and (Ca,Mg)(V,Ti)2O5; 3) ground state of pure and perturbed geometrically frustrated systems LiV2O4, (Y,Sc)Mn2, CePt2Sn2; and 4) magnetic properties of linear chains and 2-leg ladders in the hybrid (La,Sr,Ca)14Cu24O41.The muon spin relaxation experiments are performed at TRIUMF, magnetic susceptibility measurements at Columbia and neutron scattering studies at JAERI. The results of this research will be of importance in magnetism, and in physical theory. They may lead to new methods that can be applied in chemistry and in nanoscale electronic devices. This research program is interdisciplinary in nature and involves one or more graduate or postgraduate students, who receive excellent training in preparation for careers in industry, government laboratories or academia. ***