Ordering Process and Dynamics of "Ceramics"

“陶瓷”不仅是我们日常生活中常见和熟悉的材料，也是现代前沿科学技术中必不可少的重要材料。在结构上，它是由单晶颗粒组成的，这些单晶颗粒通过中间的随机表面相互强耦合。“规整”与“不规整”在这样一种材料中以不同的几何尺度共存，其本质特征是一种异质的层次结构。为了研究有序过程，有必要研究所谓的10^<-2 3>A介观团簇的动力学方面。因此，我们已经开发了一种高灵敏度的非线性磁响应观测系统，该系统对激励交流磁场的非线性磁响应具有从亚毫赫到基赫兹的宽频率范围和从毫赫到基赫兹的宽幅度变化范围。然后，我们将其应用于氧化高tc超导体、石墨嵌入化合物等，并研究了有序过程和动力学方面。CoCl_2-GIC和NiCl_2-GIC的实验结果表明，非线性响应是研究这种“陶瓷”中分层连续跃迁性质和中间相动力学结构的有效探针。在我们的研究中，首先区分了从晶内到晶间的分层超导转变。然后发现非线性响应在这些过渡点处表现出不同的奇点。事实证明，非线性磁化率是区分真正的超导玻璃和所谓的规范玻璃的重要指标，是研究josephson型相互作用性质或超导性微观起源的重要物理量。

"Ceramics" are not only popular and familiar materials in our daily life but also essentialy important one for the modern frontier science and technology. Strucuturally, it is composed of grains of a single crystal which are strongly coupled to each other through an intermediary random surface. "Regularity" and "irregularity" coexist with different geometrical scales in such a material, the essense of which is characterized by a heterogeneous hierarchical structure. In order to study the ordering process, it is essential to examine the dynamical aspect of so called mesoscopic clusters of 10^<-2 3>A.We have, therefore, developed an high-sensitive observation system of nonlinear magnetic responses to an excitation AC field of a wide frequency range from sub-mili up to kiro Hz and of a wide range of amplitude variable from mili to kiro Oe. Then, we have applied it to oxide high-Tc superconductors, graphite intercalation compounds and so on and studied the ordering processes and the dynamical aspects. The experimental results on CoCl_2-GIC and NiCl_2-GIC revealed that nonlinear response is an efficient probe to investigate the nature of hierarchical successive transitions and the dynamical structure os intermediate phase in such "ceramics". In our study, the hierarchical superconductive transitions from intra-to inter-grain direction was first well distinguished separately. The nonlinear response was then found to show different singularitioes at these transition points. From the facts, nonlinear susceptibility has been proved to be an important probe which distinguishes a true superconductive glass from a so called gauge glass and thus to be an essential physical quantity to look after the nature of Josephson-type interactions or the microscopic origin of superconductivity.