Investigation for the pressure-induced anomalous magnetism of the low dimensional organic quantum spin systems

低维有机量子自旋系统压力引起的反常磁性研究

• 批准号: 14540341
• 负责人: TAKAGI Seishi
• 金额: $ 2.11万
• 依托单位: Kyushu Institute Of Technology
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2002
• 资助国家: 日本
• 起止时间: 2002 至 2003
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14540341/
• 关键词: quantum spin system; Haldane materials; quantum ladder materials; spin-Peierls materials; magnetism under pressure; pressure-induced anomalous magnetism; 加圧下単結晶

Spin-gap systems where singlet-ground states are observed because of significant quantum effect have attracted attention in the field of low-dimensional quantum spin materials and organic magnets. We have precisely measured the magnetization and magnetic susceptibility for an organic low-dimensional quantum spin system under pressure and found the anomalous magnetic behavior. The magnetic susceptibility of a typical spin-Peierls substance, MEM-[TCNQ]_2, under pressure increases with decreasing temperature at low temperatures and it is roughly described by Cuire's law.We have studied to clarify such anomalous magnetic behavior under pressure for two years. Three kinds of spin-gap systems, (1)Haldane substance Ni(C_5H_<14>NQ_2)_2N_3PF_6, (2)quantum ladder substances : Cu_2(C_6H_<12>N_2)_2Cl_4 and related substances, (3)spin-Peierls substances : MEM-[TCNQ]_2 and a related substance, were treated in this study. Good single crystals were made and their magnetic properties were measured precisely as a function of pressure. As a result of the measurement for a single crystal under uniaxial pressure, we found that the magnetic properties of MEM-[TCNQ]_2 show significant anisotropy. In order to clarify the origin of the increase of the magnetic susceptibility under pressure for MEM-[TCNQ]_2, we have measured the electron-spin-resonance (ESR) spectra under uniaxial pressure by using a hand-made pressure cell for a conventional X-band ESR instrument : The temperature dependence of the ESR spectra show that there are two different spins under pressure, which has been supposed by the macroscopic measurement such as the magnetization and magnetic susceptibility.

由于显着的量子效应而观察到单线态基态的自旋能隙系统在低维量子自旋材料和有机磁体领域引起了人们的关注。我们精确测量了有机低维量子自旋系统在压力下的磁化强度和磁化率，发现了异常的磁行为。典型的自旋佩尔斯物质MEM-[TCNQ]_2在低温下压力下的磁化率随着温度的降低而增加，大致可以用居尔定律描述。我们已经研究了两年来澄清压力下这种反常的磁行为。三种自旋带隙体系，(1)霍尔丹物质Ni(C_5H_<14>NQ_2)_2N_3PF_6，(2)量子梯物质：Cu_2(C_6H_<12>N_2)_2Cl_4及相关物质，(3)自旋佩尔斯物质：本研究中对 MEM-[TCNQ]_2 和相关物质进行了处理。制成了良好的单晶，并精确测量了它们的磁性与压力的函数关系。通过单轴压力下对单晶的测量，我们发现MEM-[TCNQ]_2的磁性能表现出显着的各向异性。为了阐明MEM-[TCNQ]_2在压力下磁化率增加的根源，我们使用传统的手工压力盒测量了单轴压力下的电子自旋共振（ESR）谱。 X波段ESR仪器：ESR光谱的温度依赖性表明，在压力下存在两种不同的自旋，这是磁化强度和磁化率等宏观测量所假设的。

项目成果

Y.Mori, S.Takagi et al.: "Proton NMR Study of a Random-Bond Ladder Cu_2(C_5H_<12>N_2)_2(C_<1-x>Br_x)_4"Physica. B329-333. 990-991 (2003)

Y.Mori、S.Takagi 等人：“随机键梯 Cu_2(C_5H_12>N_2)_2(C_<1-x>Br_x)_4 的质子核磁共振研究”物理学。

K.Ejima, S.Takagi et al.: "Pressure Effect on the Structure of an spin-Peierls Substance : MEM-[TCNQ]_2"Physica. B329-333. 1195-1196 (2003)

K.Ejima、S.Takagi 等人：“压力对自旋 Peierls 物质结构的影响：MEM-[TCNQ]_2”物理学。

S.Takagi, K.Ejima et al.: "Anisotropic pressure dependence of the magnetism of a spin-Peierls substance : MEM-[TCNQ]_2"J.Magn.Magn.Mater.. 272-276. 1072-1073 (2004)

S.Takagi、K.Ejima 等人：“自旋 Peierls 物质磁性的各向异性压力依赖性：MEM-[TCNQ]_2”J.Magn.Magn.Mater.. 272-276。

H.Deguchi, Y.Mori, S.Watanabe, T.Tajiri, M.Mito, S.Takagi: "Pressure-induced antiferromagnetic order in a quantum spin liquid system Cu_2(C_5H_<12>N_2)_2Br_4"J.Magn.Magn.Mater.. 272-276. 952-953 (2004)

H.Deguchi、Y.Mori、S.Watanabe、T.Tajiri、M.Mito、S.Takagi：“量子自旋液体系统 Cu_2(C_5H_<12>N_2)_2Br_4 中的压力诱导反铁磁序”J.Magn。

S.Takagi, K.Ejima, M.Yamashita, T.Tajiri, M.Yoshihiro, M.Mito, H.Deguchi: "Anisotropic pressure dependence of the magnetism of a s in-Peierls substance : MEM-[TCNQ]_2"J.Magn.Magn.Mater.. 272-276. 1072-1073 (2004)

S.Takagi、K.Ejima、M.Yamashita、T.Tajiri、M.Yoshihiro、M.Mito、H.Deguchi：“Peierls 内物质的磁性的各向异性压力依赖性：MEM-[TCNQ]_2”J