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

具有竞争相互作用的复杂自旋系统的相变及其性质对观测时间和空间尺度的依赖性

• 批准号: 09640423
• 负责人: ITO Atsuko
• 金额: $ 1.98万
• 依托单位: GRADUATE SCHOOL OF HUMANITIES AND SCIENCES OCHANOMIZU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1998
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09640423/
• 关键词: Fe_xCo_<1-x>TiO_3; Fe_xMn_<1-x>TiO; muSR; magnetization; ac-susceptibilitiy; neutron magnetic scattering; competing exchange interaction; competing anisotropy; 中性子錯乱; FexMn1-xTiO3; MxMg1-xTiO3(M=Mn,Fe); FexCo1-xTiO3

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

一般来说，随机磁体根据观察的时间和空间尺度表现出多种形式的特性。在这个项目中，我们通过观察以下量来研究自旋玻璃（SG）系统，团簇玻璃（CG）系统和竞争各向异性系统：（1）低场直流磁化，（2）高场区域磁化，（3）交流磁化率，（4）中子磁散射和（5）muSR光谱，每个量都使用不同时间和空间尺度的方法进行测量。 观察。下面，我们总结了主要结果。 [A] SG 和 CG 系统 (I) 在 SG 系统 Fe_xMn_<1-x>TiO_3 上，我们测量了 M_<ZFC>-T 平面（H=const）和 M_< ZFC>-H 平面（T=const）中零场冷却磁化强度 M_<ZFC> 在一定时间 tw 内的长时间弛豫，并在 tw 后增加 T（或 H）。 M_<ZFC> 对 T(或 H) 增加的响应表明 M_<ZFC> 是 (T,H) 的函数。这似乎与 M_<ZFC> 在 T 和 H 处长期弛豫的存在不一致。然而，我们认为这些事实反映了 SG 系统复杂特性的多种形式。 (2)当M_<ZFC>(T,H)的值相同时，即使通过不同的过程达到M_<ZFC>(T,H)，M_<ZFC>(T,H)的弛豫也类似地进行。我们推断，耕耘现象在SG(CG)系统中很常见。 (3) 在M_<ZFC>的磁化过程中，当H的扫频大于临界值时，M_<ZFC>跳跃到场冷值M_<FC>，这可以用多谷结构的分层组织模型来解释。 (4)通过考察T循环和H循环对CG体系Fe_xMg_<1-x>TiO_3磁化弛豫现象的影响，建议CG体系也可以用分级组织模型来解释。 (5) muSR测量表明，CG系统在冻结温度Tf附近的临界区域比SG系统宽得多，这是由于在远高于Tf的温度下形成磁团簇所致。 [B]在竞争各向异性体系Fe_xCo_<1-x>TiO_3中，首次显示了自旋随角异型跃迁的发生，并伴随着横向自旋分量和纵向自旋分量的伸长和减少。这表明正交自旋分量是耦合的。较少的

项目成果

A.Fukaya: "Spin Dynamics of the Diluted Antiferromagnets Mn_xMg_<1-x>TiO_3 by muSR Method" Hyperfine Interactions. (in press). (1999)

A.Fukaya：“通过 muSR 方法研究稀释反铁磁体 Mn_xMg_<1-x>TiO_3 的自旋动力学”超精细相互作用。

J.Satooka: "The Relaxzation Phenomena of the Cluster-Glass Fe0.26Zn0.74F2." J.Magn.Magn.Mater.177-181. 103-104 (1998)

J.Satooka：“簇状玻璃 Fe0.26Zn0.74F2 的弛豫现象。”

A.Fukaya: "Spin Dynamics of the Diluted Antiferromagnets Mn_xMg_<1-x>TiO_3 by μSR Method" Hyperfine Interactions. (in press). (1999)

A.Fukaya：“通过 μSR 方法研究稀释反铁磁体 Mn_xMg_<1-x>TiO_3 的自旋动力学”超精细相互作用（1999 年出版）。

A.Fukawa: "Neutron Scattering Study of the Spin-Glass Mn_<0.55>Mg_<0.45>TiO_3 under Magnetic Fields." J.Phys.Chem.Solids. (in press). (1999)

A.Fukawa：“磁场下自旋玻璃 Mn_<0.55>Mg_<0.45>TiO_3 的中子散射研究。”

A.Ito: "Magnetization Process of the Mixed Compound with Exchange Frustrations Fe(). _<65>Mn_<0.35>TiO_3 and Fe_<0.50>TiO_3 -Anomalous Dependence on the Sweep-Rate of Magnetic Fields." J.Phys.Soc.Jpn.66. 3636-3647 (1997)

A.Ito：“具有交换抑制 Fe() 的混合化合物的磁化过程。_<65>Mn_<0.35>TiO_3 和 Fe_<0.50>TiO_3 - 磁场扫描速率的异常依赖性。”