High Time Resolution μSR Study with Intense DC Muon Beam

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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