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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），其中超导性、磁性和晶格动力学密切相关。当RE=Ho时，超导转变温度（Tc=7K）接近磁转变温度（T_N=5K），超导和磁性的温度与磁场相图很复杂，涉及重入超导相和反铁、亚铁、铁和不通约磁性相。本项目的目的是通过超声波测量和单轴应力下的晶格变形，通过“晶格”阐明HoNi_2B_2C的超导性和磁性之间的相互关系。我们仔细检查了浮区红外炉制备的单晶超导性的样品依赖性，发现多个超导相经常… 更多超声波测量表明，与沿[110]的应变相关的弹性常数C_<66>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 c 平面内 Ho 磁矩的铁磁涨落耦合。与沿[001]的应变相关的弹性常数C_<33>随着温度从80K降低到T_N而表现出类似的软化，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。我们推导出 c 面之间的交换相互作用对 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。该速率比水压中的速率大1个数量级。另一方面，在当前精度内，T_N 不会因沿[001]的应力而变化。我们没有发现各个方向上的应力对 Tc 有任何明显的变化。除了上述研究之外，我们还在 Spring-8 中使用同步加速器辐射进行了初步的 X 射线磁散射实验。我们通过磁布拉格散射证实了 2 K 时反铁磁相和亚铁磁相的周期性。较少的