PHASE TRANSITIONS OF COMPLICATED SPIN SYSTEMS WITH COMPETING INTERACTIONS AND DEPENDENCY OF THEIR PROPERTIES ON TIME-AND SPACE-SCALES OF OBSERVATIONS

一般来说，随机磁铁根据观测的时间和空间尺度显示出多种属性。在这个项目中，我们研究了自旋玻璃(SG)系统、团簇玻璃(CG)系统和竞争各向异性系统，观测了以下几个量：(1)低场直流磁化，(2)高场磁化，(3)交流磁化率，(4)中子磁散射，(5)MuSR谱，每个量都是用不同时间和空间尺度的观测方法测量的。下面，我们对主要结果进行总结。[A]SG和CG系统(I)在SG系统Fe_xMn_&lt；1-x&gt；TiO_3上，我们测量了在M_&lt；ZFC&gt；-T平面(H=const)和M_&lt；ZFC&gt；-H平面(T=const)的零场冷磁化强度M_(&t)的长时间弛豫，并在此之后增加了T(或H)。M&lt；ZFC&gt；对T(或H)增加的响应表明，M&lt；ZFC&gt；是(T，H)的函数。这似乎与Cons…存在的长期放松不一致然而，我们认为这些事实反映了SG系统复杂性质的多方面。(2)当M_&lt；ZFC&>(T，H)的值相同时，即使M_&lt；ZFC&>(T，H)是通过不同的过程达到的，M_&lt；ZFC&>(T，H)的松弛过程也是相似的。我们推断TILLS现象在SG(CG)系统中是普遍存在的。(3)在磁化过程中，当H的扫描速率大于临界值时，M_&lt；ZFC&gt；跃迁到场冷值M_&lt；Fc&gt；，这可以用多值结构的层次组织模型来解释。(4)从T循环和H循环对CG系统Fe_xMG_&lt；1-x&GT；TiO_3磁化驰豫现象的影响的考察中，建议CG系统也可以用层次组织模型来解释。(5)MuSR测量表明，CG系统在冻结温度Tf附近的临界区比SG系统的要宽得多，这是由于在远高于Tf的温度下形成了磁团簇所致。[B]在竞争各向异性体系FexCo&lt；1-x&gt；TiO3中，首次发现了伴随着横向自旋分量和纵向自旋分量的伸长和减少而发生的自旋翻转转变。这表明相互垂直的自旋分量是耦合的。较少

In general, random magnets show multiform properties depending on time- and space-scales of observation. In this project, we investigated spin-glass(SG) systems, cluster-glass(CG) systems and competing anisotropy systems by observing the following quantities (1) low-field dc-magnetization, (2) magnetization up to high-field region, (3) ac-susceptibility, (4) neutron magnetic scattering and (5) muSR spectra, each of which was measured by using methods with different time- and space-scales of observation. Below, we summarize the main results. [A] SG and CG systems (I) On the SG system Fe_xMn_<1-x>TiO_3, we measured long-time relaxations of zero-field-cooled magnetization M_<ZFC> in the M_<ZFC>-T plane(H=const) and the M_< ZFC >-H plane(T=const) for a certain time tw and after tw we increased T(or H). The response of M_<ZFC> for the increase of T(or H) indicates that M_<ZFC> is a function of (T,H). This seems inconsistent with the existence of the long-time relaxation of M_<ZFC> at a cons … More tant T and H.However, we consider that these facts reflect the multiform sides of the complicated properties of SG systems. (2) When the value of M_<ZFC>(T,H) is the same even if M_<ZFC>(T,H) is reached by the different process, the relaxation of M_<ZFC>(T,H) proceeds similarly. We infer that tills phenomenon is common in SG(CG) systems. (3) In the magnetization process of M_<ZFC>, when the sweep-rate of H is larger than the critical value, M_<ZFC> jumps to the field-cooled value M_<FC>, which is explained by the hierarchical organization model with multi-valey structures. (4) From the examination of the effects of the T-cycle and the H-cycle on the relaxation phenomenon of magnetizations for the CG system Fe_xMg_<1-x>TiO_3, the CG system is suggested to be explained also by the hierarchical organization model. (5) The muSR measurement has clarified that the critical region of CG system around the freezing temperature Tf is much wider than that of SG system, which is due to the formation of magnetic clusters at temperatures much higher than Tf. [B] In the competing anisotropy system Fe_xCo_<1-x>TiO_3, the occurrence of the spin-flop transition accompanied with the elongation and the reduction of the transverse spin component and the longitudinal one was firstly shown. This indicates that the orthogonal spin components are coupled. Less