Optical Evidence of Itinerant-Localized Crossover of 4f4f Electrons in Cerium Compounds

Cerium (Ce)-based heavy-fermion materials have a characteristic double-peak structure (mid-IR peak) in the optical conductivity [$\sigma(\omega)$] spectra originating from the strong conduction ($c$)--$f$ electron hybridization. To clarify the behavior of the mid-IR peak at a low $c$-$f$ hybridization strength, we compared the $\sigma(\omega)$ spectra of the isostructural antiferromagnetic and heavy-fermion Ce compounds with the calculated unoccupied density of states and the spectra obtained from the impurity Anderson model. With decreasing $c$-$f$ hybridization intensity, the mid-IR peak shifts to the low-energy side owing to the renormalization of the unoccupied $4f$ state, but suddenly shifts to the high-energy side owing to the $f$-$f$ on-site Coulomb interaction at a slight localized side from the quantum critical point (QCP). This finding gives us information on the change in the electronic structure across QCP.Comment: 6 pages, 4 figures. To appear in JPSJ (Letters

Superconductivity and physical properties of Ba24Si100 determined from electric transport, specific-heat capacity, and magnetic susceptibility measurements

Both Ba24Si100 and Ba24Ge100 with crystallographically identical structure are found to be superconducting at 1.4 and 0.27 K, respectively. Physical properties of this superconductor Ba24Si100 are studied by electric transport, specific heat capacity, and magnetic susceptibility measurements. The density of states at the Fermi level NEF=0.148 states eV-1(Siatom)-1 and a distinct jump of Cp at the superconducting transition temperature ΔCp=0.272JK-1mol-1 are obtained. An exponential fit of Cp below the superconducting states gives an energy gap 2Δ=0.423meV and shows that this is a superconductor having s-wave character or isotropic energy gap. On the basis of our experimental data other important physical parameters are also derived

Comparison of magnetization transfer contrast of conventional and simultaneous multislice turbo spin echo acquisitions focusing on excitation time interval

Image contrast differs between conventional multislice turbo spin echo (conventional TSE) and multiband turbo spin echo (SMS-TSE). Difference in time interval between excitations for adjacent slices (SETI) might cause this difference. This study aimed to evaluate the influence of SETI on MT effect for conventional TSE and compare conventional TSE with SMS-TSE in this respect

SMS-TSE sequenceとConventional TSE sequenceのMT効果の比較・検討

Multi-band sequence can obtain multi slices simultaneously. Relation between simultaneous multi-slice (SMS) turbo spin echo and MT effect were investigated by changing slice excitation time interval. As a result, SMS showed larger MT effect than conventional technique.第45回日本磁気共鳴医学会大