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

9802000上村这个实验研究项目致力于研究纯和掺杂的自旋能隙系统以及自旋-液体系统中的反常磁行为，如用Muon自旋驰豫研究的那样。主要感兴趣的是低维和/或几何上受挫的自旋系统。令人感兴趣的是自旋冻结的形成/不存在的条件，受挫的作用，以及电荷掺杂和磁稀释的影响。1)准一维之字形自旋链SrCuO2和LixV2O5中的有序温度和/或有序矩尺寸的问题；2)二支梯状物中的电荷/空位掺杂效应；3)纯和微扰几何受阻体系LiV2O4，(Y，Sc)Mn2，CePt2Sn2的基态；以及4)杂化的(La，Sr，Ca)14Cu24O41中线性链和二支梯的磁性。介子自旋弛豫实验在TRIUMF进行，磁化率测量在哥伦比亚大学进行，中子散射研究在JAERI进行。这一研究项目本质上是跨学科的，涉及一名或多名本科生或研究生，他们接受了为在工业、政府实验室或学术界就业做准备的出色培训。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中的异常磁性行为。令人感兴趣的问题是样品中磁性物种的局域行为，在这项工作中使用了一种先进的实验方法--Muon自旋弛豫。测量必须在一个特殊的加速器设施中进行，在那里产生µ介子并注入到感兴趣的样品中。测量揭示了样品内部那些位置的磁场强度，通常接近内部磁矩，在这些位置上，介子在衰变之前就被捕获了。令人感兴趣的是自旋冻结的形成/不存在的条件，受挫的作用，以及电荷掺杂和磁稀释的影响。1)准一维之字形自旋链SrCuO2和LixV2O5中的有序温度和/或有序矩尺寸问题；2)二支梯子中的电荷/空位掺杂效应；3)纯和微扰几何受阻体系LiV2O4、(Y，Sc)Mn2、CePt2Sn2的基态；4)杂化化合物(La，Sr，Ca)14Cu24O41中直链和二柱阶梯的磁性。介子自旋弛豫实验在TRIUMF进行，磁化率测量在哥伦比亚大学进行，中子散射研究在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级的电子设备。这一研究项目本质上是跨学科的，涉及一名或多名本科生或研究生，他们接受了为在工业、政府实验室或学术界就业做准备的出色培训。***

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. ***