arXiv subjects

H. Hosono

Publications and source records attributed to H. Hosono.

58 records · Page 4Linked to original sources

arXiv2008

Spin Ordering in LaOFeAs and Its Suppression in Superconductor LaO0.89F0.11FeAs Probed by Mössbauer Spectroscopy

The 57Fe Mössbauer spectroscopy was applied to an iron-based layered superconductor LaO0.89F0.11FeAs with a transition temperature of 26 K and its parent material LaOFeAs. Throughout the temperature range from 4.2 to 298 K, a singlet spectrum with no magnetic splitting was observed as a main component of each Mössbauer spectrum of the F-doped superconductor. No additional internal magnetic field was observed for the spectrum measured at 4.2 K under a magnetic field of 7 T. On the other hand, the parent LaOFeAs shows a magnetic transition at around 140 K, and this temperature is slightly lower than that of a structural phase transition from tetragonal to orthorhombic phase, which accompanies the resistivity anomaly at around 150 K. The magnetic moment is estimated to be ~0.35 $μ$B/Fe at 4.2 K in the orthorhombic phase, and the spin disorder remains in the magnetic ordered state even at 4.2 K. The fact that no magnetic transition in LaO0.89F0.11FeAs was observed even at 4.2 K under 7 T implies a strong spin fluctuation above Tc or small magnetic moment in this system. Therefore, the present results show that the F-doping effectively suppresses the magnetic and structural transitions in the parent material and the suppression leads to emergence of superconductivity in this system.

cond-mat.supr-con↗

arXiv2006

Temperature Dependence of the Chemical Potential in NaxCoO2: Implications for the Large Thermoelectric Power

We have performed a temperature-dependent photoemission study of a NaxCoO2 (x~0.8) epitaxial thin film prepared by the reactive solid-phase epitaxy method. The chemical potential shift as a function of temperature was derived from the Co 3d peak shift, and revealed a crossover from the degenerate Fermion state at low temperatures to the correlated hopping state of Co3+/Co4+ mixed-valence at high temperatures. This suggests that the large thermoelectric power at high temperatures should be considered in the correlated hopping picture.

cond-mat.str-el↗

arXiv2006

Potential Profiling of the Nanometer-Scale Charge Depletion Layer in n-ZnO/p-NiO Junction Using Photoemission Spectroscopy

We have performed a depth-profile analysis of an all-oxide p-n junction diode n-ZnO/p-NiO using photoemission spectroscopy combined with Ar-ion sputtering. Systematic core-level shifts were observed during the gradual removal of the ZnO overlayer, and were interpreted using a simple model based on charge conservation. Spatial profile of the potential around the interface was deduced, including the charge-depletion width of 2.3 nm extending on the ZnO side and the built-in potential of 0.54 eV.

cond-mat.mtrl-sci↗

arXiv2004

Observation of Jonscher Law in AC Hopping Conduction of Electron-Doped Nanoporous Crystal 12CaO7Al2O3 in THz Frequency Range

We have performed terahertz time-domain spectroscopy of carrier-doped nanoporous crystal 12CaO7Al2O3 showing the Mott variable range hopping at room temperature. The real part of the dielectric constant clearly demonstrates the nature of localized carriers. The frequency dependence of both the real and imaginary parts of the dielectric constant can be simply explained by assuming two contributions: a dielectric response by the parent compound with no carriers and an AC hopping conduction with the Jonscher law generally reported up to GHz range. The possible obedience to the Jonscher law in the THz range suggests a relaxation time of the hopping carriers much faster than 1ps in the carrier-doped 12CaO7Al2O3.

cond-mat.mtrl-sci↗