High Time Resolution μSR Study with Intense DC Muon Beam

在加拿大的TRIUMF学习材料科学的各种科目。强烈的直流μ介子束使我们获得了高时间分辨率的μSR，这是日本独特的μ介子装置（KEK-MSL）的脉冲μ介子束所不能达到的。进行了以下μSR实验：研究了一种新型超导材料YNi_2B_2C，其横向场μSR高达5T。通过对单晶样品混合态（磁线晶格相）中μ子观测到的场分布的精确分析，推导出了磁穿透深度λ和涡旋核半径ρv。λ随磁场线性增加。而ρv则随着场的增大而急剧减小，在高场处趋于平稳。利用高质量的单晶CuO，在零场条件下，在中间磁相（216K-232K）观测了相干介子自旋进动。在反铁磁有序相中，精确地确定了局部内部磁场，包括其温度、更强的自然依赖性和方向。对CeRh_2Si_2进行了高达0.6GPa的高压μSR处理。这个样品很有趣，因为它在环境压力下显示出36K（T_N）的磁相变，但T_N随着压力的增加而减少，并进入超导相。为了在μSR实验中实现更高的压力，需要进行更多的开发，并且正在进行中。由三维电子组成的LiV_2O_4的Knight位移测量显示出重费米子特征，在超低温下发现了两个不等效的V位。用μSR对层状化合物Cu(OH)X的磁性有序态进行了研究。用进动频率的个数（X=Cl， Br为2个，X=I为1个）证实了磁结构的差异。采用激光光泵浦实现砷化镓中介子原子复极化的建议被接受并进行了实验，但效果不显著。设置需要进一步改进。利用负介子对铈化合物进行了研究。成功地观察到金属铈中的μ^-SR信号。少

Various subjects in material science were studied at TRIUMF in Canada. The intense DC muon beam enables us a high time resolution μSR, which is beyond the capability with the pulsed muon beam at the unique muon facility in Japan (KEK-MSL). The following μSR experiments were performed. A novel superconducting material YNi_2B_2C was studied with transverse field μSR up to 5T.From the precise analysis of field distribution observed by muon in the mixed state (flux line lattice phase) of the single crystal sample, magnetic penetration depth λ and vortex core radius ρv was deduced. λ increases linearly with magnetic field. On the contrary ρv shrinks steeply with increasing field and subsequently levels off at higher field. Using a high quality single crystal CuO, coherent muon spin precession was observed at the intermediate magnetic phase (216K-232K) under zero field. In the antiferromagnetic ordered phase, the local internal magnetic fields were determined precisely, inclusively its tempe … More rature dependence and its orientations. High pressure μSR was performed on the CeRh_2Si_2 up to 0.6GPa. This sample is interesting because it shows a magnetic phase transition at 36K(T_N) under ambient pressure but T_N decreases with pressure and goes into a superconducting phase. To achieve higher pressure in μSR experiment more developments are necessary and are under way. From the Knight shift measurement in LiV_2O_4, which shows heavy fermion feature in spite of consisting from 3d-electrons, two unequivalent sites of V were found at ultra low temperature. Layered compounds Cu(OH)X were studied by μSR in its magnetic ordered state. The difference of magnetic structure was confirmed with the number of precession frequencies (two for X=Cl, Br, one for X=I). The proposal to achieve the repolarization of muonic atom in GaAs by laser optical pumping was accepted and experiments were performed but with no significant effect. Further improvement in the set up is needed. Ce compounds study using negative muon was started. μ^-SR signal in metallic cerium was successfully observed. Less