权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Deviation from the S-state of Eu^<2+> ion in magnetic materials due to relativistic effect of f electrons

由于f电子的相对论效应导致磁性材料中Eu^<2>离子的S态偏离

基本信息

批准号：
63540256
负责人：
KAWAKAMI M.
金额：
$ 0.96万
依托单位：
Department of Physics, Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1989
项目状态：
已结题

项目摘要

It is known that the excited states generally mix into the ground state of f electrons by the relativistic effect. Since Eu^<2+> ion has the ground S state which is spherically symmetric, the effect can be easily seen. In this study we tried to find this effect through the observation of the quadrupole splitting in the NMR spectrum of the Eu nuclei. The splitting is proportional to the electric field gradient at the nuclei, which consists of the lattice contribution and the contribution arising from the asymmetry of the electronic charge of the Eu atom itself. We studied EuX (X=O, Te) of the cubic NaCl type, in which the lattice contribution is very small. Using a single crystal of EuTe, we observed ^<151>Eu and ^<153>Eu NMR spectrum in liquid helium temperatures in magnetic fields up to 21 kOe by means of the steady state method. Above 6 kOe, ^<151>Eu NMR exhibited a single line, but ^<153>Eu NMR exhibited a five-line splitting which attributable to the quadrupole interaction. The variation of the spectrum with the crystal direction was measured. The spectrum for [100] was symmetric. The magnitude of the splitting decreased rather rapidly with increasing temperature. The relativistic effect could not be separated, but with the use of the value from the previous ENDOR measurements of Eu^<2+> in CaF_2 we analyzed the magnitude of the quadrupole splitting as a sum of the relativistic effect and the contribution from the magnetoelastic effect. The analysis gave important information of the magnetostriction in antiferromagnetic EuTe. For EuO the splitting was not observed, which indicates that the sample used was not so pure. The temperature dependence of the splitting in EuSe was also presented.

众所周知，激发态通常通过相对论效应混合到f电子的基态中。由于Eu ^ 2+ 离子具有球对称的基S态，因此可以容易地看到效果。在这项研究中，我们试图通过观察铕核核磁共振谱中的四极分裂来发现这种效应。分裂与原子核处的电场梯度成正比，该电场梯度由晶格贡献和Eu原子本身电荷不对称性引起的贡献组成。我们研究了立方 NaCl 型的 EuX (X=O, Te)，其中晶格贡献很小。使用EuTe单晶，我们通过稳态方法在液氦温度和高达21 kOe的磁场中观察到^ 151 Eu和^ 153 Eu NMR谱。高于6kOe， 151 Eu NMR表现出单谱线，但153 Eu NMR表现出五谱线分裂，这归因于四极相互作用。测量了光谱随晶体方向的变化。 [100] 的光谱是对称的。随着温度的升高，分裂的幅度相当快地减小。相对论效应无法分离，但利用之前 CaF_2 中 Eu^2+> 的 ENDOR 测量值，我们将四极分裂的幅度分析为相对论效应和磁弹性效应贡献的总和。该分析提供了反铁磁 EuTe 中磁致伸缩的重要信息。对于EuO，没有观察到分裂，这表明所用的样品不那么纯。还提出了 EuSe 分裂的温度依赖性。