Understanding of Mechanism for Superconductivity on f-electron Superconductors with No Inversion Symmetry by High-pressure NMR

本课题的主要目的是研究CePt_3Si反铁磁态超导能隙的电子学信息和铁磁态UIr在高压下的微观超导特性。首先，我们通过反复试验找到了CePt_3Si中Ce、Pt和Si的最佳化学计量比。在此之后，我们在外场下测量了取向样品上的Si和Pt的NMR谱。所得到的结果与以前报道的中子衍射研究的磁结构不一致。接下来，我们测量了CePt3Si和非磁性LaPt3Si在宽温度范围内的核弛豫速率的温度依赖性。奇怪的是，La系统的弛豫速率高于Ce系统。这两个重要的核磁共振结果将被清楚地记录下来，并将在一些期刊上发表。还测量了奈特位移通过超导转变温度（Tc）的温度依赖性。平行于c轴的Knight位移，即自旋磁化率没有显示出任何变化，这导致CePt3Si中的奇宇称库珀对。太长的相干长度使我们无法找到低于Tc的核弛豫速率的详细行为，即使通过场循环NMR进行。因此，在不久的将来，我们应该尝试用最佳的场循环测量参数来重新测量弛豫率。不幸的是，我们不能找到Ir NMR信号在UIr的铁磁和顺磁状态，虽然已经成功地找到Ir信号在其他参考样品。无论如何，CePt3Si和UIr的样品对于超导和正常状态下的异常行为都非常重要，因此我们计划进行NMR实验，以暂时找到有趣的结果。(298字）

The purpose of this project is the following two issues : one is to get the electronic information on the superconducting energy gap appearing in the antiferromagnetic state of CePt3Si, the other is to get the microscopic superconducting character of ferromagnetic UIr under high pressure. First of all, we found the best stoichiometry of Ce, Pt and Si in CePt3Si by trial and error. After that we measured the NMR spectra for Si and Pt on the aligned sample under external field. The obtained results were not consistent with the magnetic structure reported previously by the neutron diffraction study. Next, we measured the temperature-dependence of nuclear relaxation rate for the wide temperature range on CePt3Si and non-magnetic LaPt3Si. Strangely enough, the relaxation rate of La system is higher than that of Ce system. Both important NMR results will be clearly explaned, which will be published in some journals. The temperature dependence of Knight shift through the superconducting transition temperature (Tc) was also measured. The Knight shift, namely the spin susceptibility, parallel to the c-axis did not show any change, which leads to the Cooper-pairs of odd parity in CePt3Si. Too long coherence length prevented us from finding the detailed behavior of nuclear relaxation rate just below Tc, even if performed by the field-cycling NMR. So we should try to measure again the relaxation rate with best parameters for the field-cycling measurements in the near future. Unfortunately, we could not find Ir NMR signals in UIr for the ferromagnetic and paramagnetic states, although already succeeded in finding Ir signals in other reference samples. Anyhow, both samples of CePt3Si and UIr are so important for unusual behaviors in the superconducting and normal states that we plan to perform the NMR, experiments to find interesting results for the time being. (298 words)