A study on magnetic excitation and phase separation in the vicinity of the quantum critical point(QCP) in the strongly correlated electron system(SCES)

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The aim of this program is to investigate the magnetic fluctuations around QCPs in cuprate, cobaltate, and ruthenate compounds, and heavy-fermion compounds including Ce,Yb and U ions using microscopic experimental techniques. Here, the QCP is the physical condition where the phase transition temperature is suppressed to the absolute zero by varying a physical parameter. Near the QCP, non-Fermi-liquid behavior is observed, which deviates from ordinary behaviors seen in normal metals. We use nuclear magnetic resonance (NMR) and muon spin resonance/rotation (μSR) as our microscopic experimental techniques. We have emphasized the use of μSR experiments when an NMR experiment is impossible due to the short relaxation time beyond the NMR experimental limit or in extremely low fields. We showed that the two experimental techniques are quite complementary to each other. In addition, we investigated the interplay between magnetism and unconventional superconductivity in the SCES from the microscopic point of view using NMR and μSR measurements.During the research period, we investigated the following subjects,a)magnetic fluctuations near the QCPb)the relation between magnetism and superconductivity in cuprate and HF compounds.c)Knight shift measurements in recently-discovered superconductorsd)Hydrate cobaltate superconductor.The results during the period are summarized, and are published as shown in the next page.