Time-and Space-Scale Dependent Properties of Spin Systems with Exchange Frustrations

我们认为，为了提取自旋玻璃(SG)系统的多种性质，综合应用不同时间和空间尺度的观测技术是有用的。在这个项目中，我们使用以下技术研究了五个短程SG系统(见下文)：(1)低去磁场磁化，(2)交流磁化率，(3)穆斯堡尔谱，(4)中子散射，(5)muSR，和(6)直到高场区的磁化过程。经检验的样本如下。(A)磁性非稀释系：典型的伊辛系Fe_xMn_&lt；1-x&gt；TiO_3；类海森堡系Ni_xMn_&lt；1-x&gt；TiO_3。(B)稀释系：伊辛系Fe_xZn_&lt；1-x&gt；F_2和Fe_xMG_&lt；1-x&gt；TiO_3，以及类海森堡系Mn_xMG_&lt；1-x&gt；TiO_3。(1)确定了x-T磁相图的细节。(2)为De-Almeida-Thouless理论提供了实验支持。(3)我们发现这些现象与考虑的…是一致的此外，在场冷条件下达到的自旋态是稳定的，自旋系统形成了具有许多山谷结构的层次化组织。(4)在SG-冻结温度(TSG)以下，自旋仍有起伏，这归因于横向自旋分量的存在。(5)通过观察非线性极化率的发散行为，认为重入相变是一种相变。(2)Ni_xMn_&lt；1-x&gt；TiO_3：我们首次实验观察到具有弱自旋各向异性的类海森堡体系中的正交自旋分量在不同温度下相继冻结(x=0.42，0.47)。(3)Fe_&lt；0.26&gt；Zn_&lt；0.74&gt；F_2和Fe_&lt；0.2&gt；Mg_&lt；0.8&gt；TiO_3：SG在2T&lt；SG&gt；因此，我们已经确定这两个系统都是典型的团簇玻璃。我们推断，在浓度接近渗流浓度的稀释体系中，这种冻结机制对SG-冻结是常见的。(4)MnxMG；lt；1-x&gt；TiO3：基本确定了x-T磁相图。我们发现，自旋系统在x-0.57处从一个显示随机场效应的AF系统转变为一个SG系统。较少

We have considered that, in order to extract multiform properties of spin-glass (SG) systems, a combined application of various techniques with different time-and space-scale of observation is useful. In this project, we investigated five short-range SG systems (see below) using the following techniques : (1) low-de-field magnetization, (2) ac-susceptibility, (3) Mossbauer spectra, (4) neutron scattering, (5) muSR,and(6) magnetization process up to high-field region. The samples examined are as follows. (A) Magnetically non-diluted system : typical Ising system Fe_xMn_<1-x>TiO_3, and Heisenberg-like system Ni_xMn_<1-x>TiO_3. (B) Diluted systems : Ising systems Fe_xZn_<1-x>F_2 and Fe_xMg_<1-x>TiO_3, and Heisenberg-like system Mn_xMg_<1-x>TiO_3. The followings are summary of our results. (1) Fe_xMn_<1-x>TiO_3 : (1) Details of x-T magnetic phase diagram was decided. (2) Experimental supports for de-Almeida-Thouless theory were given. (3) We found the phenomena consistent with the consider … More ation that the spin state reached under field-cooled conditions is stable, and the spin system forms a hierarchical organization with many valley structures. (4) Below SG-freezing temperature (TSG) , fluctuations of spins remain, which is attributed to the existence of the transverse spin component (5) The reentrant transition was suggested to be a phase transition by observing the divergent behavior of non-linear susceptibility. (2) Ni_xMn_<1-x>TiO_3 : We firstly observed with experiments that the orthogonal spin components in a Heisenberg-like system with weak spin anisotropy freeze succesively at different temperatures (x=0.42,0.47) . (3) Fe_<0.26>Zn_<0.74>F_2 and Fe_<0.2>Mg_<0.8>TiO_3 : SG-freezing was shown to occur among AF-clusters which were formed at temperatures higher than 2T_<SG>. Thus, we have identified that both systems are a typical cluster glass. We infer that this mechanism is common to SG-freezing occurring in diluted systems with concentrations near below the percolation concentration. (4) Mn_xMg_<1-x>TiO_3 : The x-T magnetic phase diagram was determined on the whole. We have found that the spin system changes at x-0.57 from an AF-system showing the random-field effect to an SG-system. Less