Studies on Quantum Magnets by Alternating and Ladderlike Chains

我们研究了一些镍、铜配合物，它们被认为是S=1反铁磁键交替链、S-1/2和1自旋交替链、S=1/2铁磁-铁磁-反铁磁-反铁磁链（F-F-AF-AF）链，S=1/2的两条腿自旋梯和S=1/2的锯齿形链。我们对S=1/2的两条腿自旋梯和S=1/2的锯齿形链进行了磁化率和磁化强度测量。1键交替链，并将实验结果与计算结果进行了比较。然后，键交替比和交换常数进行了评估。本研究中的一些显著发现是观察到对应于磁化量子化的1/2磁化平台，以及通过观察某种镍键交替链化合物中的无隙行为来实验验证Affleck-Halfmann猜想。此外，我们还得到了S=1键交替链中单重态-二聚体基态的证据。第二和第三个化合物与量子亚铁磁体的研究有关。在每种化合物中，磁化率乘以温度的温度依赖性是亚铁磁链的典型特征。在S=1/2的F-F-AF-AF链状化合物中，我们观察到了饱和场附近磁化强度的急剧增加，并根据极短的关联长度对其进行了讨论;在S=1/2的双梯形化合物中，我们进行了磁化率和比热的测量，并与计算结果进行了比较.在有间隙的阶段，实验和计算之间的协议是优秀的，而协议变得穷人在无间隙的阶段，这可能是描述的Tomonaga-Luttinger液体。我们讨论了最近的理论和核磁共振实验方面的这种偏差。

We investigated some nickel and copper complexes which are regarded as the S=1 antiferromagnetic bond alternating chains, the S-1/2 and 1 spin alternating chain, the S=1/2 ferromagnetic-ferromagnetic-antiferromagnetic-antiferromagnetic (F-F-AF-AF) chain, the S=1/2 two-leg spin ladder and the S=1/2 zigzag chain.We performed susceptibility and magnetization measurements on the S=1 bond alternating chains and compared the experimental results with the calculated ones. Then, the bond alternating ratios and the exchange constants are evaluated. Some of the remarkable findings in this study are the observation of the 1/2 magnetization plateau which corresponds to the quantization of magnetization and the experimental verification of the Affleck-Haldane conjecture by the observation of the gapless behavior in a certain nickel bond alternating chain compound. Moreover, we got evidence for the singlet-dimer ground state in an S=1 bond alternating chain.The second and the third compounds are related to the studies on quantum ferrimagnets. The temperature dependence of magnetic susceptibility times temperature in each compound is typical of the ferrimagnetic chain. In the S=1/2 F-F-AF-AF chain compound, we observed a steep increase of magnetization around the saturation field and discussed it in terms of the extremely short correlation length.For the S=1/2 two-leg ladder compound, we performed susceptibility and specific heat measurements and compared the results with the calculated ones. In the gapped phase, the agreement between the experiment and the calculation is excellent, while the agreement becomes poor in the gapless phase that is probably described by the Tomonaga-Luttinger liquid. We discussed this deviation in terms of a recent theory and a NMR experiment.