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

w：\awards\awards96\*.doc 9802000 Uemura 这个实验研究项目致力于在纯和掺杂的自旋间隙系统，并在自旋液体系统中的不寻常的磁性行为，作为研究的μ子自旋弛豫。 主要的兴趣是低维和/或几何挫折自旋系统。感兴趣的是自旋冻结的形成/不存在的条件，挫折的作用，以及电荷掺杂和磁稀释的影响。更详细地说，感兴趣的四个主题和系统是：1）准一维之字形自旋链中的有序温度和/或有序矩大小问题 SrCuO 2和LixV 2 O 5;（2）双梯结构Sr_2（Cu，Zn）_4 O_6，LaCuO_（2.5），（Ca，Mg）（V，Ti）_2 O_5中的电荷/空位掺杂效应;（3）纯的和微扰的几何阻挫体系LiV_2 O_4，（Y，Sc）Mn_2，CePt_2Sn_2的基态;（4）杂化体系（La，Sr，Ca）_（14）Cu_（24）O_（41）中线性链和双梯结构的磁性。 μ子 自旋弛豫实验在TRIUMF进行，磁化率测量在哥伦比亚和中子散射 研究 在杰瑞。 这 研究 程序 是跨学科的性质，涉及一个或多个研究生或研究生 学生，谁获得优秀 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的晶体样品中的异常磁性行为。感兴趣的问题是样品中磁性物质的局域行为，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介子并注入感兴趣的样品中。测量揭示了样品内部这些位置的磁场强度，通常靠近内部磁矩，μ子在衰变之前被捕获。感兴趣的是自旋冻结的形成/不存在的条件，挫折的作用，以及电荷掺杂和磁稀释的影响。 详细地说，我们感兴趣的四个主题和系统是：1）准一维之字形自旋链SrCuO_2和Li_xV_2 O_5的有序化温度和/或有序矩大小问题; 2）电荷/空位掺杂效应 在 两条腿 梯子 Sr2（Cu，Zn）4O6， LaCuO 2.5， 和（Ca，Mg）（V，Ti）2O5; 3)基态纯 和 μ子自旋弛豫实验在TRIUMF进行，磁化率测量在哥伦比亚进行，中子散射实验在JAERI进行。这项研究的结果将在磁学和物理理论中具有重要意义。 它们可能会导致新的方法，可以应用于化学和纳米电子器件。 该研究计划是跨学科的性质，涉及一个或多个研究生或研究生，谁在工业，政府实验室或学术界的职业生涯准备接受良好的培训。 ***

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. ***