STUDY OF QUANTUM SPIN EFFECTS IN BOND ALTERNATING CHAIN AND SPIN LADDER SYSTEMS USING MOLECULE-BASED MAGNETIC COMPLEXES.

使用基于分子的磁复合体研究键交替链和自旋梯系统中的量子自旋效应。

• 批准号: 07640468
• 负责人: AJIRO Yoshitami
• 金额: $ 1.34万
• 依托单位: KYUSHU UNIVERSITY (1996)University of Fukui (1995)
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1995
• 资助国家: 日本
• 起止时间: 1995 至 1996
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640468/
• 关键词: Low Dimensional Magnet; Quantum Spin; Haldane System; Spin-Peierls System; Bond Alternating Chain; Spin Ladder; Spin Gap; Model Compound; 交互型反強磁性; 梯子型反強磁性

The purpose of the present research is to elucidate the quantum spin effects in low dimensional magnets, especially in bond alternating chain and spin ladder systems using molecule-based magnetic complexes. We performed various experiments including nuclear magnetic resonance (NMR), electron spin resonance (ECR), neutron scattering, muon spin relaxation (uSR), high field magnetization as well as susceptibility and specific measurements. We obtained the following results.1.Study of quantum effects of composite spin systems composed of S=1/2 subelements.(1) We studied new quantum spin effects in one-dimensional S=1/2 trimer systems, 3CuCl_2・dioxane and A_3Cu_3(PO_4)_4, in which ferromagnetic or antiferromagnetic trimers composed of three S=1/2 spins are respectively, weakly coupled antiferromagnetically in one dimension. We found peculiar magnetic properties characteristic of composite spin systems with nonuniform spatial structure.(2) We performed the susceptibility, high field magnetiz … More ation and NMR measurements on a S=1/2 alternating linear chain system CuCl_2・2picolin, uniform linear chain systemCuBr_2・2picolin and their mixed compounds CuCl_<281-x)>Br_<2x>・2picolin (0<x<1). We founda systematic change in singlet-ground-state properties as a function of composition as a result of a formation or destruction of the quantum spin gap due to the effects of bond alternation and randomness.2.Study of singlet-ground-state in antiferromagnetic quantum spin chains.(1) We performed a systematic study on the impurity effects on the intimately related quantum states in the Haldane and spin-Peierls systems, S=1 NiC_2O_4・2DMIz and S=1/2 CuGeO_3. We found that the SP state is very unstable and the broken SP state results in the appearance of the antiferromagnetic staggered moments, while the Haldane state is stable against nonmagnetic impurity doping up to 20%.(2) We performed the ESR measurements on the Zn-doped NENP,S=1 Haldane system with nonmagnetic impurities. A new interpretation was proposed that observed signals are due to the S=1/2 broken valence bond which is subjected to the field-induced staggered internal fields produced by the underlying antiferromagnetic lattice.(3) We studied the S=1 quasi-one dimensional Heisenbergantiferromagnet CsNiCl_3 which undergoes 3D ordering at T_N=4.8K,in order to revel the effect of the interchain coupling on the Haldane state. We found that the Haldane state really exists in the 1D phase above T_N. We confirmed the S=1/2 edge states characteristic of the Haldane state and revealed a crossover from the quantum to classical regimes as a function of both temperature and magnetic field. Less

本研究的目的是利用分子基磁性配合物阐明低维磁体中的量子自旋效应，特别是键交替链和自旋阶梯体系中的量子自旋效应。我们进行了各种实验，包括核磁共振（NMR）、电子自旋共振（ECR）、中子散射、介子自旋弛豫（uSR）、高场磁化以及磁化率和特异性测量。我们得到了以下结果。S=1/2子元组成的复合自旋系统的量子效应研究。(1)研究了由3个S=1/2自旋组成的铁磁性或反铁磁性三聚体在一维反铁磁性弱耦合体系、3CuCl_2·二恶烷和A_3Cu_3(PO_4)_4中新的量子自旋效应。我们发现了具有非均匀空间结构的复合自旋体系特有的磁性。(2)对S=1/2交替线性链体系CuCl_2·2picolin、均匀线性链体系cubr_2·2picolin及其混合化合物CuCl_<281-x)>Br_<2x>·2picolin （0<x<1）进行了磁化率、强磁场、磁化率和核磁共振测量。我们发现由于化学键交替和随机性的影响，量子自旋间隙的形成或破坏导致单重态基态性质作为组成函数的系统变化。反铁磁量子自旋链中单重态基态的研究。(1)系统地研究了杂质对Haldane和自旋- peierls体系S=1 NiC_2O_4·2DMIz和S=1/2 CuGeO_3密切相关量子态的影响。我们发现SP态是非常不稳定的，SP态的破碎会导致反铁磁交错矩的出现，而Haldane态在非磁性杂质掺杂高达20%的情况下是稳定的。(2)对含非磁性杂质的掺锌NENP，S=1霍尔丹体系进行了ESR测量。提出了一种新的解释，即观测到的信号是由于S=1/2价键断裂所致，这是由底层反铁磁晶格产生的场诱导交错内场造成的。(3)研究了S=1准一维海森堡反铁磁体CsNiCl_3在T_N=4.8K下发生三维有序，揭示了链间耦合对Haldane态的影响。我们发现在T_N以上的1D相中确实存在霍尔丹态。我们证实了霍尔丹态的S=1/2边缘态特征，并揭示了从量子态到经典态的交叉作为温度和磁场的函数。少

项目成果

M.Takigawa: "Static properties of the S=1 one-dimensional antiferromagnet AgVP_2S_6" phys,Rer,B. 52. 12526-12529 (1995)

M.Takikawa：“S=1 一维反铁磁体 AgVP_2S_6 的静态特性”phys，Rer，B。

Xun,Xu: "The disordeucl magnetic structure in the triangular-lattice XY antferromagnet CsMnBr_3" J.Phys : Condens.Matter. 8. 4065-4070 (1996)

Xun,Xu：“三角晶格XY反铁磁体CsMnBr_3中的无序磁结构” J.Phys : Condens.Matter。

Y.AJIRO: "ESR of the magnetic dangling bond in the Haldane state" J.phy,Soc.Jpn.66(in press). (1997)

Y.AJIRO：“Haldane 态磁悬键的 ESR”J.phy,Soc.Jpn.66（印刷中）。

Y.Ajiro: "Impurity effect on the ground-state spin configuration in triangular lattice antiferromagnet CuFeO_2" J.Phys.Soc.Jpn.64. 3643-3646 (1995)

Y.Ajiro：“三角晶格反铁磁体 CuFeO_2 中基态自旋构型的杂质效应”J.Phys.Soc.Jpn.64。

O.Tchernyshyov: "Spin-Peierls and spin glass phases in pure and doped CuGeO_3 : A uSR study" J.Mag.Mag.Mater.140-144. 1687-1688 (1995)

O.Tchernyshyov：“纯 CuGeO_3 中的自旋 Peierls 和自旋玻璃相：一项 uSR 研究”J.Mag.Mag.Mater.140-144。