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

目前的工作是为了阐明多极相互作用在稀土化合物的磁性中的作用。 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是由准二维四极相互作用驱动的，这些相互作用由沿四方C轴沿着四方C轴和弱铁极（FQ）相互作用组成。 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，已经澄清的是，4F的基础状态和40 K处的第一个兴奋状态都是单人，并且AFM过渡和现场引起的AFQ过渡关注与4F级别有关4F级别，包括较高的兴奋状态，包括较高的兴奋状态，即150 k，即相位过渡是一个交换范围的vleck磁过渡。 TBB_2C_2是AFM订单和抗Fiferro-Octupolar（AFO）订单的共存阶段。 TBB_2C_2和稀释系统的异常磁性行为已根据TBB_2C_2的（AFQ+AFO）基态令人满意地理解