NMR Studies of Quantum Choherence and Magnetism in Spin-Ladder Systems

自旋梯系统中量子相干性和磁性的核磁共振研究

基本信息

批准号：
09440138
负责人：
KITAOKA Yoshio
金额：
$ 8.58万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

This research project was planed to investigate by means of NMR/NQR the quantum coherence and anoma-lous magnetism in S=1/2 spin-ladder systems through the impurity and carrier doping effects.Characteristics of impurity (Zn, Ni, and La)-induced staggered polarization (IISP) and antiferromagnetic long-range order (AF-LRO) were clarified in gapped spin-1/2 Heisenberg two-leg ladder compound SrCu^2O^3. A correlation length xi^3/a estimated from a quasi-one-dimensional (Q1D) IISP along the two-leg was found to be much longer even in x=0.001 and 0.005 than xi^0/a. The T-independent xi^3/a is scaled to an average distance D^<AV> = 1/(2x) in the Zn and Ni doping and D^<AV> = 1/x in the La doping between the impurities, for example, xi^0/a -50 is estimated in the Zn doping when D^<AV> = 500 for x=0.001. The significantly broadened NQR spectrum has unambiguously identified the appearance of AF moments associated with the AF-LRO in the Zn and Ni doping. Rather uniform AF moments around the middl … More e Cu sites between the impurities are estimated to be in an order of 0.04 mubeta at 1.4 K with their direction along the a axis. The spatial variation of AF moments is shown to be of exponential type with almost the same xi^0/a = 8 (x=0.01) and 4.5 (x=0.02) as in the LISP for the Zn doping. The Q1D-IISP was found to be dramatically enhanced by an interladder interaction even though so weak, once the impurity breaks up the quantum coherence in the short-range resonating valence bond (RVB) state with the gap. On the other hand, we propose that T^N is determined by a strength of the interladder interaction and a size of S^o. We showed that hole-doped two-leg ladder compound Sr^<2.5>Ca^<11.5>Cu^<24>O^<41> comprising Cu^2O^3 ladders and CuO^2 chains reveals three dimensional (3D) magnetic order below T^M=2.2 K.We found that small moments - 0.02 mubeta are spontaneously ordered on the ladders, whereas large moments - 0.56mubeta or the magnetic Cu sites occupying about one-fourth of the chains. It is suggested that this 3D magnetic order is a cooperative phenomenon driven by the formation of pinned CDW-like state on the ladders which the optical conductivity measurement has clarified. Less

该研究项目计划通过NMR/NQR通过杂质和携带者掺杂效应S = 1/2旋转 - 循环系统中的量子相干性和异常磁性进行调查。海森伯格两腿阶梯化合物srcu^2o^3。从X = 0.001和0.005的相关长度xi^3/a沿两腿沿准二维（Q1D）IISP估计的时间比XI^0/a更长。 t非依赖性xi^3/a在Zn和ni掺杂中的平均距离d^<av> = 1/（2x），以及d^<av> = 1/x在杂质之间的la掺杂中，例如，xi^0/a -50在d^<av> = 500时估计Zn掺杂在Zn掺杂中。显着拓宽的NQR光谱已明确鉴定出与Zn和Ni掺杂中AF-LRO相关的AF矩的出现。相当统一的AF矩在中间……杂质之间的更多E CU位点在1.4 K时为0.04 mubeta，其方向沿着轴为方向。 AF矩的空间变化显示为指数类型，几乎相同的xi^0/a = 8（x = 0.01）和4.5（x = 0.02）与Zn掺杂的LISP中。发现Q1D-IISP通过间隔相互作用而动态增强，即使杂质分解了与间隙的短距离谐振价键（RVB）状态中的量子相干性。另一方面，我们建议T^n取决于间阵的强度和s^o的大小。 We showed that hole-doped two-leg ladder compound Sr^<2.5>Ca^<11.5>Cu^<24>O^<41> compliing Cu^2O^3 ladders and CuO^2 chains reveals three dimensional (3D) magnetic order below T^M=2.2 K.We found that small moments - 0.02 mubeta are sponsored and ordered on the ladders, whereas large moments - 0.56 mubeta或占用链约四分之一的磁性CU位点。建议通过在梯子上形成类似CDW的状态，这是一种合作的现象驱动器，光电导率测量已被阐明。较少的