Lattice anomaly associaterd with the magnetic order in a re-entrant superconductor Ho_<1-x>Y_xNi_2B_2C

重入超导体 Ho_<1-x>Y_xNi_2B_2C 中与磁序相关的晶格异常

基本信息

批准号：
14540331
负责人：
ASAI Kichizo
金额：
$ 1.92万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

项目摘要

In RNi_2B_2C(R=rare earth elements) the superconductivity and the magnetic order of the rare-earth elements coexist, (or compete), where the superconductivity, the magnetism, and the lattice dynamics are closely related to the others. When RE =Ho, the superconducting transition temperature (Tc=7K) is close to the magnetic transition temperature (T_N=5K), and the temperature vs magnetic-field phase diagram for the superconductivity and the magnetism is complicated involving the reentrant superconducting phase and antiferro-, ferri-, ferro-, and incommensurate magnetic phases. The purpose of the present project is to elucidate the interrelation between the superconductivity and the magnetism of HoNi_2B_2C through "lattice" by the ultrasonic measurement and by lattice deformation under uniaxial stresses.We carefully checked the sample dependence of the superconductivity of the single crystals prepared by a froating-zone infraned furnace, and found that multiple superconducting phases ofte … More n coexist even in a single crystal.The Ultrasonic measurements revealed that the elastic constant C_<66>, relevant to the strain along [110], shows a large softening up to 60% with decreasing temperature from 80 K to T_N. We conclude that the strain couples with the ferromagnetic fluctuation of Ho magnetic moments within the c-plane. The elastic constant C_<33>, relevant to the strain along [001], shows a similar softening with decreasing temperature from 80 K to T_N although its change is smaller by two orders of magnitude than C_<66>. In addition, C_<33> shows stepwise softenings associated with the meta-magnetic transitions at 2 K. We conclude that the strain along [001] couples with the magnetic correlation of Ho magnetic moments between the c-planes. We deduced the dependence on the c-spacing of the exchange interactions between the c-planes.The magnetic measurements under uniaxial stress revealed that T_N increases remarkably by applying a stress along [110]. The rate is larger by 1 order of magnitude than that in the hydro-pressure. On the other hand, T_N dose not change by the stress along [001] within the present precision. We did not find any appreciable change of Tc by the stresses in all directions.In addition to the above investigation, we performed preliminary x-ray magnetic scattering experiment using synchrotron radiation in Spring-8. We confirmed the periodicity of the antiferro- and ferri- magnetic phases at 2 K by magnetic Bragg scattering. Less

在RNi_2B_2C(R=稀土元素)中，稀土元素的超导性和磁序共存(或竞争)，其中当RE =Ho时，超导性、磁性和晶格动力学密切相关。，超导转变温度（Tc=7K）接近磁转变温度（T_N=5K），并且温度与磁场相图为超导性和磁性是复杂的，涉及重入超导相和反铁相、铁相、铁相和不通约磁相。本项目的目的是通过“晶格”阐明HoNi_2B_2C的超导性和磁性之间的相互关系。超声波测量和单轴应力下的晶格变形。我们仔细检查了样品依赖性研究人员对浮区红外炉制备的单晶的超导性进行了研究，发现即使在单晶中，多个超导相也经常共存。超声波测量表明，弹性常数 C_<66> 与沿 [ [110]，随着温度从 80 K 降低到 T_N，软化程度高达 60%。我们得出结论，应变与 Ho 磁矩的铁磁涨落耦合。 c 面。与沿 [001] 的应变相关的弹性常数 C_<33> 随着温度从 80 K 降低到 T_N，显示出类似的软化，尽管其变化比 C_<66> 小两个数量级。此外，C_<33> 显示出与 2 K 时的超磁转变相关的逐步软化。我们得出结论，沿 [001] 的应变与 c 面之间的 Ho 磁矩的磁相关性耦合。推导出c面之间交换相互作用对c间距的依赖性。单轴应力下的磁测量表明，沿[110]施加应力，T_N显着增加，速率比中的大1个数量级。另一方面，在目前的精度范围内，T_N 不会因沿 [001] 的应力而变化。在上述研究中，我们利用 Spring-8 中的同步加速器辐射进行了初步的 X 射线磁散射实验，通过磁布拉格散射证实了 2 K 下的反铁磁相和亚铁磁相的周期性。