Competitive Antiferroquadrupolar and Antiferromagnetic Interactions in Tetragonal Rare-earth Compounds RB_2C_2.

四方稀土化合物RB_2C_2中的竞争性反铁四极和反铁磁相互作用。

基本信息

批准号：
12304017
负责人：
YAMAGUCHI Yasuo
金额：
$ 29.36万
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：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

Growth of single crystals, identification of crystal structure and various measurements such an magnetic susceptibility, magnetization, specific heat, electric resistivity, Mossbauer effect and neutron scattering have been performed is order to clarify antiferroquadrupolar (AFQ) interaction and ordering in tetragonal RB_2C_2 compounds.Precise magnetic phase diagrams were determined no DyB_2C_2 with an AFQ ordering temperature of T_Q=24.3 K and an antiferromagnetic (AFM) one of T_N=l5.3 K and HoB_2C_2 with the reverse transition sequence of T_N=5.8 K and T_Q=5.0 K. The AFM, AFQ or their coexistent structure in every phase was also determined by neutron diffraction on single crystals in magnetic fields. Moreover, it was revealed that anomalous phase diagrams of the AFM TbB_2C_2 with T_N=21.7 K originates in occurrence of field-induced AFQ ordering transitions, and the AFM and AFQ structures of their field-induced phases were also clarified.The magnetic phase of T_Q≦T≦T_N in HoB_2C_2 whic … More h is adjacent to (AFM+AFQ) phase has some resemblance to that (phase IV) in cubic (Ce,La)B_6 that the character has been mysterious and controversial. It has been also found that the AFM phase of TbB_2C_2 is very similar to phase IV in the both compounds and that phase IV appears in (Dy,Gd)B_2C_2 where the transition sequence is the same to that in HoB_2C_2. Phase IV strongly attract us and is the most important target in future research in this field because of its mysterious character which might be affected strongly by octupolar interactions. Phase IV has been found in four compounds, and we found three of them in the RB_2C_2 compounds.Combination of neutron diffraction and ^<161>Dy Mossbauer experiments gave the important information that the strong AFQ interaction mediates along the tetragonal c-axis like a pseude-one-dimmensional interaction while the AEM interactions act strongly in the C-plane. The competition of these AFQ and AFM interactions causes various and anomalous magnetic properties in RB_2C_2. Less

单个晶体的生长，晶体结构的鉴定和各种测量结果，例如进行磁化易感性，磁化，特定的热，电阻，摩斯鲍尔效应和中子散射，是为了澄清抗反核核（AFQ）的相互作用（AFQ）相互作用（AFQ）相互作用以及在四方RB_2C_2 COMPONS AN NO and AN NO and AN NON NO aN NO dyb_22 complo digog_22 T_Q = 24.3 K和抗fiferromagnetic（AFM）T_N = L5.3 K和HOB_2C_2，其反向过渡序列T_N = 5.8 K和T_Q = 5.0 K. AFM，AFM，AFM或其在每个阶段的共有结构也由单个磁场中的中子差异确定。此外，揭示了T_N = 21.7 K的AFM TBB_2C_2的异常相图起源于现场诱导的AFQ订购过渡的发生，以及其现场诱导阶段的AFM和AFQ结构。在Cutic（CE，LA）B_6中，该角色一直是神秘和有争议的。还发现，TBB_2C_2的AFM相与两种化合物中的IV相非常相似，并且该相IV出现在（DY，GD）B_2C_2中，其中过渡序列与HOB_2C_2中的过渡序列相同。第四阶段强烈吸引我们，是该领域未来研究中最重要的目标，因为它的神秘特征可能会受到八极极性相互作用的强烈影响。第四阶段已在四种化合物中发现，我们在RB_2C_2化合物中发现了其中三个，中子衍射的combination和 ^<161> dy Mossbauer实验提供了重要的信息，表明强烈的AFQ相互作用沿着四方C轴介导，例如Pseude-One-nigmensients Itactions and emem互动，同时又有强劲的相互作用。这些AFQ和AFM相互作用的竞争会导致RB_2C_2中的各种异常磁性。较少的