Experimental Research on Roles of Quadrupolar and Octupolar Interactions in Magnetism of Rare Earth Compounds.

四极和八极相互作用在稀土化合物磁性中作用的实验研究。

基本信息

批准号：
16204021
负责人：
ONODERA Hideya
金额：
$ 29.7万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16204021/
关键词：
Orbital Order Antiferromagnetic Order Antiferroquadrupolar Order Antiferro-octupolar Order Magnetic Structure Magnetic Phase Transition Magnetic Phase Diagram Van Vleck Magnetic Transition 反強四極子相互作用反強磁性相互作用八極子相互作用 DyB_2C_2 TbB_2C

项目摘要

The present works have been performed with the aim of clarifying the roles of multipolar interactions in the magnetism of rare earth compounds. The results are summarized as follows.1.We found out a new phase transition and completed the complicated phase diagrams of DyB_2C_2 that had been found by us to show the successive antiferroquadrupolar (AFQ) and antiferromagnetic (AFM) transitions.2.Neutron diffraction experiments on the Y-diluted DyB_2C_2 single-crystals have revealed that the quadrupolar ordering in DyB_2C_2 is driven by quasi-one-dimensional quadrupolar interactions which consist of extremely strong AFQ interactions along the tetragonal c-axis and weak ferroquadrupolar (FQ) interactions in the basal c-plane. Moreover, the ^<161>Dy Mossbauer experiments, the neighboring Y ion decreases or increases the ^<161>Dy magnetic hyperfine fields depending on the substituted site because of the change of frustration between the AFQ and AFM interactions.3.The substitution of 20%Dy by Gd brought forth a new transition sequence in which the AFQ transition occurs below the AFM transition temperature.4.By the Y-dilution of TbB_2C_2, it has been clarified that both the 4f ground state and the first excited state at 40 K are singlets and that the AFM transition and the field-induced AFQ transition concern with the 4f levels including the higher excited states around 150 K, that is, the phase transition is a exchange-induced Van Vleck magnetic transition.5.The precise examination on the Gd-diluted TbB_2C_2 has revealed that the ground state of TbB_2C_2 is a coexistent phase of AFM order and antiferro-octupolar (AFO) order. The anomalous magnetic behaviors of TbB_2C_2, and the diluted system have been understood satisfactorily based on the (AFQ+AFO) ground state of TbB_2C_2

目前的工作旨在阐明多极相互作用在稀土化合物磁性中的作用。主要结果如下：1.发现了新的相变，并完成了我们所发现的DyB_2C_2的复杂相图，以显示连续的反铁四极（AFQ）和反铁磁（AFM）转变。2.中子衍射实验对 Y 稀释的 DyB_2C_2 单晶的研究揭示了 DyB_2C_2 中的四极有序性是由准一维四极相互作用，由沿四方 c 轴的极强 AFQ 相互作用和基础 c 平面中的弱铁四极 (FQ) 相互作用组成。此外，在 ^<161>Dy Mossbauer 实验中，由于 AFQ 和 AFM 相互作用之间的挫败变化，相邻 Y 离子根据取代位点减少或增加 ^<161>Dy 超精细磁场。 3. 取代20%Dy by Gd 产生了一个新的转变序列，其中 AFQ 转变发生在 AFM 转变温度以下。4.通过 TbB_2C_2 的 Y 稀释，它已经澄清了 4f 基态和 40 K 处的第一激发态都是单线态，并且 AFM 跃迁和场诱导 AFQ 跃迁与 4f 能级有关，包括 150 K 附近的更高激发态，即相位5.对Gd稀释的TbB_2C_2的精确检验表明，TbB_2C_2的基态是AFM 级和反铁八极（AFO）级共存相。基于TbB_2C_2的(AFQ+AFO)基态，对TbB_2C_2的异常磁行为和稀释系统有了满意的理解