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

具有交换挫败的自旋系统的时间和空间尺度相关特性

• 批准号: 04452039
• 负责人: ITO Atsuko
• 金额: $ 4.48万
• 依托单位: OCHANOMIZU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1992
• 资助国家: 日本
• 起止时间: 1992 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452039/
• 关键词: Spin-glass; Reentrant spin-glass; Cluster-glass; Low-field -dc-magnetization; Non-linear susceptibility; Mossbauer spectra; muSR; High-field magnetization process; リエントラントスピングラス; MSR; ランダム磁性体; ランダムフラストレーション系; 高磁場磁化過程; 希釈反強磁性体; ランダム磁場; 中性子散乱

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

我们认为，为了提取自旋玻璃（SG）系统的多种形式的属性，各种技术与不同的时间和空间尺度的观察的组合应用是有用的。在这个项目中，我们研究了五个短距离SG系统（见下文）使用以下技术：（1）低磁场磁化，（2）交流磁化率，（3）穆斯堡尔谱，（4）中子散射，（5）muSR，（6）磁化过程高场区。检查的样品如下。(A)非磁稀释体系：典型的Ising体系Fe_xMn_<1-x>TiO_3和类Heisenberg体系Ni_xMn_<1-x>TiO_3。(B)稀释体系：Ising体系Fe_xZn_<1-x>F_2和Fe_xMg_<1-x>TiO_3，类Heisenberg体系Mn_xMg_<1-x>TiO_3。以下为我们的业绩摘要。(1)Fe_xMn_<1-x>TiO_3：（1）确定了详细的x-T磁相图。(2)给出了de-Almeida-无边界理论的实验支持。(3)我们发现这些现象与我们认为的 ...更多信息 场冷条件下达到的自旋态是稳定的，并且自旋系统形成具有许多谷结构的分级组织。(4)在SG冻结温度（TSG）以下，自旋的涨落仍然存在，这归因于横向自旋分量的存在。（5）通过观察非线性磁化率的发散行为，认为重入转变是一种相变。(2)Ni_xMn_<1-x>TiO_3：我们首次在实验上观察到弱自旋各向异性的类海森堡系统中的正交自旋分量在不同温度（x= 0.42，0.47）下发生冻结。(3)Fe_<0.26>Zn_<0.74>F_2和Fe_<0.2>Mg_<0.8>TiO_3：SG的凝固发生在高于2 T_2时形成的AF团簇之间<SG>。因此，我们已经确定，这两个系统是一个典型的集群玻璃。我们推断，这种机制是常见的SG-冻结发生在稀释的系统中，浓度接近低于渗滤浓度。(4)Mn_xMg_<1-x>TiO_3：基本确定了x-T磁相图。我们发现在x = 0.57时，自旋系统从具有无规场效应的AF系统转变为SG系统。少

项目成果

H. Kawano: "Two Successive Spin Glass Transitions in Nondiluted Heisenberg-Like Spin Glass Nio.42Mn0.58TiO3." J. Phys. Soc. Jpn.62. 2575-2578 (1993)

H. Kawano：“未稀释的类海森堡自旋玻璃 Nio.42Mn0.58TiO3 中的两个连续自旋玻璃转变。”

E. Torikai: "μ^+SR Study of Ising Spin-Glass Fe0.5Mn0.5TiO3." Hyperfine Interactions. 84. 105-108 (1994)

E. Torikai：“伊辛自旋玻璃 Fe0.5Mn0.5TiO3 超精细相互作用的 μ^+SR 研究。”

A. Ito: "Studies of Diluted Antiferromagnet Fe0.2Mg0.8TiO3:Percolation Concentration and Cluster-Glass." J. Phys. Soc. Jpn.64(NO.5 in press). (1995)

A. Ito：“稀释反铁磁体 Fe0.2Mg0.8TiO3 的研究：渗滤浓度和簇玻璃。”

A. Fukaya: "Spin-Flop Transition of the Diluted Antiferromagnet Mn_XMg_<1-X>TiO_3." Physica B. 201. 88-90 (1994)

A. Fukaya：“稀释反铁磁体 Mn_XMg_<1-X>TiO_3 的自旋翻转转变。”

A. Tobo: "Concentration-Temperature PhaseDiagram of the Diluted Antiferromagnet MnxMg_<1-X>TiO_3." J. Magn. Magn. Mater.140-144(in press). (1995)

A. Tobo：“稀释反铁磁体 MnxMg_<1-X>TiO_3 的浓度-温度相图。”