We have investigated electronic band structure of a transparent conducting oxide, Nb-doped anatase TiO2 (TNO), by means of first-principles band calculations and photoemission measurements. The band calculations revealed that Nb 4d orbitals are strongly hybridized with Ti 3d ones to form a d-nature conduction band, without impurity states in the in-gap region, resulting in high carrier density exceeding 1021 cm-3 and excellent optical transparency in the visible region. Furthermore, we confirmed that the results of valence band and core-level photoemission measurements are consistent with prediction by the present band calculations.

We have measured photoemission spectra of SrTiO3/LaTiO3 superlattices with a topmost SrTiO3 layer of variable thickness. A finite coherent spectral weight with a clear Fermi cutoff was observed at chemically abrupt SrTiO3/LaTiO3 interfaces, indicating that an "electronic reconstruction" occurs at the interface between the Mott insulator LaTiO3 and the band insulator SrTiO3. For SrTiO3/LaTiO3 interfaces annealed at high temperatures (approximately 1000 degrees C), which leads to Sr/La atomic interdiffusion and hence to the formation of La(1-x)Sr(x)TiO3-like material, the intensity of the incoherent part was found to be dramatically reduced whereas the coherent part with a sharp Fermi cutoff was enhanced due to the spread of charge. These important experimental features are well reproduced by layer dynamical-mean-field-theory calculation.

We have measured soft x-ray photoemission and O 1s x-ray absorption spectra of Ca1−xSrxRuO3 thin films prepared in situ. The coherent and incoherent parts have been identified in the bulk component of the photoemission spectra, and spectral weight transfer from the coherent to the incoherent part has been observed with decreasing x, namely, with increasing orthorhombic distortion. We propose that, while the Ru 4d one-electron bandwidth does not change with x, the distortion and hence the splitting of the t2g band effectively increases electron correlation strength. Although strong mass enhancement is found in the electronic specific heat data, the coherent part remains wide, suggesting enhanced band narrowing only in the vicinity of EF . Metal-insulator transition has been extensively studied because of its fundamental importance in condensed matter physics as well as of its close relationship with remarkable phenomena such as the high-temperature superconductivity in cuprates and the colossal magnetoresistance in manganites [1]. Broadly speaking, metalinsulator transition occurs in two ways. One is bandwidth control, and the other is filling control. In bandwidth control, bandwidth and hence electron correlation strength is changed through the modification of, e.g., the lattice parameters. Recent developments of dynamical mean-field theory (DMFT) have led to a lot of progress in understanding many problems inherent in strongly correlated electron systems, including Mott metal-insulator transition [2]. According to DMFT, as U/W increases, where U is the on-site Coulomb energy and W is the oneelectron bandwidth, spectral weight is transferred from the coherent part (the quasiparticle band near E F ) to the incoherent part (the remnant of the Hubbard bands 1 − 2 eV above and below E F ) [3]. Metal-to-insulator transition thus occurs as the spectral weight of the coherent part vanishes.In perovskite-type ABO 3 compounds, bandwidth control is realized through the modification of the radius of the A site ion r A and hence the modification of the B-O-B bond angle. As r A decreases, the bond angle decreases from 180• and the cubic lattice transforms to the orthorhombic (GdFeO 3 -type) structure. The orthorhombic distortion reduces W , because the effective transfer integrals between the neighboring B sites is governed by the super-transfer process via the O 2p state. RNiO 3 (R = rare earth) is a typical example of bandwidth control systems and shows a metal-insulator transition as a

Thermomagnetic irreversibility and magnetic short range ordering in Mn 2.5 Co 0.5 O 4 tetragonal spinel thin films J. Appl. Phys. 107, 09E152 (2010); 10.1063/1.3364051 Room-temperature ferrimagnetic semiconductor 0.6 Fe Ti O 3 • 0.4 Fe 2 O 3 solid solution thin films