NMR study on competitive order in high-temperature superconductor by using clean single crystal

本研究的主要目的是用核磁共振方法揭示超净系统YBa_2Cu_4O_8（Y-1248）单晶在超导态下的竞争有序和隐序参量共存等性质的细节，主要对实验结果进行了分析，并建立了核磁共振实验的设备环境。通过对Rb_2Cu_3SnF_3单晶和Cr-黄钾铁矾单晶的核磁共振测量，以及对产生很小的Cl-NMR信号的Cu_2OCl_2粉末样品的核磁共振测量，成功地提高了微小样品的信噪比和信号灵敏度<12>。建立了单晶（甚至是微小样品）的角度相关NMR测量方法，该系统有可能应用于超净Y-1248单晶的NMR测量，以及超净Y-1248单晶的详细信息，如超导态的竞争有序和隐序参数共存等。

The main purpose of this study is to reveal the detail of the properties, such as the competitive order and co-existence with hidden order parameters in the superconductor state by using NMR method of the super clean system YBa_2Cu_4O_8, socalled Y-1248, single crystal.I have mainly analyzed the experimental results and constructed the environment of the equipment of the NMR experiments. I succeed the improvement of the signal/noise ratio and the sensitivity of signal for a minute size sample through the NMR measurement of single crystal of Rb_2Cu_3SnF_<12>, and Cr-jarosite which are minute size samples and the Cu_2OCl_2 powder samples, which generate very small Cl-NMR signal. The measurements of the angle dependence NMR of single crystal, even a very minute sample, are established.It is possible that this system is applied to NMR measurements of the super-clean system Y-1248 single crystal and detailed information of the super-clean system Y-1248 single crystal such as the competitive order and co-existence with hidden order parameters in the superconductor state.