Experimental results of electrical resistivity, magnetization and specific heat on single crystal specimens of Ce 2 Zn 17 have been reported and analyzed by means of a single ion Hamiltonian model. There appeared a sharp peak in the specific heat due to a phase transition from paramagnetic to antiferromagnetic states. The antiferromagnetic state was characterized as a lower-dimensional Ising-type. It became clear that the crystal field had a substantial effect on the magnetic susceptibility and the electrical resistivity. There was no evidence of the dense Kondo effect for the electrical resistivity. These experimental results show that Ce 2 Zn 17 is a rare cerium compound with the stable valence.
SmS undergoes a pressure-induced phase transition from a semiconducting to a mixed-valent state. Although the mixed valence state has been extensively studied, the semiconducting state with a divalent ionic state is not well understood yet. Here we report transport properties of the low-pressure semiconducting phase. Combining the thermoelectric power with the electrical resistivity, we observe that the mobility of electrons excited onto the conduction band is much greater than that of holes left behind in the valence band, the electron effective mass is nearly equal to the hole effective mass, and the relaxation time of the electron is much larger than that of the hole.
A strongly correlated insulator, samarium mono-sulfide (SmS), presents not only the pressure-induced insulator-to-metal transition (IMT) with the color change from black to golden-yellow but also current-induced IMT (CIMT) with negative resistance. To clarify the origin of the CIMT of SmS, the electronic structure change has been investigated by optical reflectivity and angle-integrated photoelectron spectra by applying an electric current. At lower temperatures than about 100 K, where the nonlinear V–I curve has been observed, the carrier density rapidly increases, accompanied by decreasing relaxation time of carriers with increasing current. Then, the direct gap size increases, and the mean valence changes from Sm2+-dominant SmS to the mixed-valent one with increasing current. These results suggest that the CIMT originates from increasing the Sm 4f-5d hybridization intensity induced by the applied current.
From detailed angle-resolved NMR and Meissner measurements on a ferromagnetic (FM) superconductor UCoGe (T_Curie ~ 2.5 K and T_SC ~ 0.6 K), we show that superconductivity in UCoGe is tightly coupled with longitudinal FM spin fluctuations along the c axis. We found that magnetic fields along the c axis (H || c) strongly suppress the FM fluctuations and that the superconductivity is observed in the limited magnetic field region where the longitudinal FM spin fluctuations are active. These results combined with model calculations strongly suggest that the longitudinal FM spin fluctuations tuned by H || c induce the unique spin-triplet superconductivity in UCoGe. This is the first clear example that FM fluctuations are intimately related with superconductivity.
Immunohistochemistry revealed initial expression of the stage-specific glyocprotein, GP68, in various mesenchymal tissue substructures of mouse embryos. During the 11-15th days of gestation, GP68 was localized in the primitive meninges, chondroblasts and perichondrium of pre-cartilaginous vertebral bodies and ribs, connective tissue cells of the dermis, the epicardium and endocardium of the heart, the epimysium and perimysium of skeleton musclature, and the basement membranes of splanchnic organs. Double staining for laminin expression indicated coincidental expression in identical tissue substructures. However, laminin was expressed in days 10-18 embryos and the neonate. Therefore, GP68 is coincidentally expressed with laminin in mesenchymal tissues between the 11th and 15th day of gestation, and may play a role as a laminin-associated protein. In the light of these results, a hypothesis concerning the relationship between these two proteins and the mechanisms of non-integrin laminin-associated proteins during normal embryogenesis is discussed further.
We have measured the uranium ${L}_{3}$ absorption and resonant emission spectra in the localized magnetic compound $\mathrm{U}{\mathrm{Pd}}_{3}$ and heavy fermion $\mathrm{U}{\mathrm{Pd}}_{2}{\mathrm{Al}}_{3}$ as a function of pressure. The spectral line shape of the absorption edge is found to vary rapidly in $\mathrm{U}{\mathrm{Pd}}_{2}{\mathrm{Al}}_{3}$ with a notable broadening of the white line above the structural transition around $25\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ while it shows a more gradual variation in $\mathrm{U}{\mathrm{Pd}}_{3}$ over the considered pressure range $(0--40\phantom{\rule{0.3em}{0ex}}\mathrm{GPa})$, indicating different responses of the $f\text{\ensuremath{-}}d$ electrons to the compressed lattice in the two compounds. The U ${L}_{3}$ absorption spectra in both $\mathrm{U}{\mathrm{Pd}}_{3}$ and $\mathrm{U}{\mathrm{Pd}}_{2}{\mathrm{Al}}_{3}$ and their pressure dependence were further simulated via first-principles band calculations within the linear muffin-tin orbital approach. The calculations reproduce the main features of the experimental absorption edges. The calculated pressure dependence of the $f$ charge reveals a stronger localization of the $f$ electrons in $\mathrm{U}{\mathrm{Pd}}_{3}$ which shows a remarkably stable valency under pressure, close the nominal value of 4. On the contrary, our results point to a mixed valent ${\mathrm{U}}^{4\ensuremath{-}\ensuremath{\delta}}$ ground state in $\mathrm{U}{\mathrm{Pd}}_{2}{\mathrm{Al}}_{3}$ at ambient conditions, evolving into a ${\mathrm{U}}^{4+}$ (or possibly ${\mathrm{U}}^{4+\ensuremath{\delta}}$) configuration at high pressure. The $f$-electron delocalization could be responsible for the known structural transition in $\mathrm{U}{\mathrm{Pd}}_{2}{\mathrm{Al}}_{3}$.
