Periodic array of metallic nanocylinder combined with the highly luminous dielectric layer is a good platform to control the intensity, spectral shape and directionality of photoluminescence (PL). In spite of its importance, the effect of cylinder height on the PL properties has not been verified experimentally. Here we investigate the effect of cylinder height on the PL properties both experimentally and numerically. The system consisted of a highly luminous layer made of Eu(III) complex and a series of periodic array of aluminum nanocylinders with different heights. The strongest directional PL was achieved when the height is similar to the diameter, i.e., the aspect ratio close to unity. Our finding is useful for designing the compact and efficient luminescence source with directional output.

Lattice volume expansion or amorphization renders EuTiO3 ferromagnetic, although the stable phase of crystalline EuTiO3 is an antiferromagnet. The lattice volume expansion is induced into the crystalline EuTiO3 thin film by utilizing the lattice mismatch between the thin film and a substrate. The magnetization at low temperatures monotonically increases with an increase in lattice volume for the crystalline EuTiO3 thin film, coincident with the results of calculations based on the hybrid Hartree–Fock density functional approach. The ferromagnetic interaction between Eu2+ ions is enhanced by the amorphization as well; the amorphous EuTiO3 thin film becomes a ferromagnet, and the Curie temperature is higher for amorphous Eu2TiO4 than for its crystalline counterpart. The phenomenon, that is, the volume expansion- and amophization-induced ferromagnetism, is explained in terms of the competition between ferromagnetic and antiferromagnetic interactions among Eu2+ ions.

Bulk EuTiO3 is known as a compound in which spin and soft phonon mode is strongly coupled. Recent theoretical study suggests that application of stress or formation of strain leads to a drastic change in magnetic and dielectric properties of EuTiO3 and that so-called multiferroic properties emerge under such a situation. In the present study, effect of strain induced by a substrate, on which EuTiO3 thin film is deposited, on the magnetic properties of the film has been experimentally examined. By using a pulsed laser deposition method, EuTiO3 thin film has been deposited on different kinds of substrate, i.e., LaAlO3, SrTiO3, and DyScO3; the lattice parameter of these compounds is smaller than, just the same as, and larger than that of EuTiO3, respectively. X-ray diffraction analysis confirms that the strain induced in the plane of as-deposited EuTiO3 thin films on different substrates is coincident with the lattice parameter of the substrate compounds. Also, all the as-deposited EuTiO3 thin films manifest elongation of lattice in a direction perpendicular to the film surface. Temperature dependence of magnetization indicates that all the thin films exhibit ferromagnetic behavior at low temperatures. The magnetization at 2 K under a magnetic field of 100 Oe is the highest for EuTiO3 on DyScO3 and the lowest for EuTiO3 on LaAlO3. The experimental result is coincident with the first-principles calculations which predict that ferromagnetic spin configuration becomes more stable as the lattice volume of EuTiO3is increased.

Polycrystalline β-Ga2O3 doped with Fe3+, (Ga1−x Fex)2O3 (x=0.02, 0.05, 0.08 and 0.1), has been prepared by a solid-state reaction. Ferromagnetic ordering is observed at room temperature for samples prepared by β-Ga2O3 and Fe(NO3)3·9H2O and sintered at low temperatures below 900 °C, while the sintering at temperatures above 900 °C leads to the paramagnetic behavior. X-ray diffraction analysis for the samples sintered at 500 °C reveals that the single phase of β-Ga2O3 can be obtained up to x=0.08 without traces of secondary phase or other impurity. Magnetization as a function of temperature shows superparamagnetic or cluster spin-glass behavior, indicating that long-range ferromagnetic ordering does not exist in the present systems. It is suggested that the inhomogeneous distribution of Fe3+ is responsible for the ferromagnetic behavior.

Second-harmonic generation of transparent glass-ceramics containing BaTiO3 crystalline phase was investigated using Maker fringe method. When 15BaO · 15TiO2 · 70TeO2 glass was heat-treated at 415 °C for 0.5–12 h, (101)- or (110)-oriented BaTiO3 crystals precipitated in the near-surface region. The resultant glass-ceramics exhibit second-harmonic generation. Variation of second-harmonic intensity with angle of incidence, i.e., the Maker fringe pattern changes drastically with an increase in heat treatment time and temperature. No second-harmonic signal was detected in glass-ceramics derived from 15SrO · 15TiO2 · 70TeO2 glass. These facts suggest that BaTiO3 crystal is responsible for the second-order nonlinear phenomenon, although its structure is closer to cubic than tetragonal according to x-ray diffraction measurements. In order to estimate second-order nonlinear optical coefficient d(2), Maker fringe patterns of the BaTiO3-containing glass-ceramics were analyzed. For the glass-ceramic after heat treatment for 0.5 h, d33 and thickness of BaTiO3-crystallized layer, L, are 3.65 pm/V and 3.43 μm, respectively. The value of second-order nonlinear optical coefficient is comparable to those of BaTiO3 films prepared via metalorganic chemical vapor deposition and pulsed-laser deposition. On the other hand, the glass-ceramic heat-treated for 12 h exhibits d15 = 0.31 pm/V and L = 300 μm. The thickness of the layer active in second-order nonlinearity evaluated from the Maker fringe pattern is coincident with the observation by scanning electron microscopy.

Intense triboluminescence has been observed in rare-earth-doped aluminosilicates such as BaAl2Si2O8and SrAl2Si2O8doped with Eu2+, Tb3+, or Dy3+. The triboluminescence is caused by the excitation of and emission from rare-earth ions doped in the crystals. A discrepancy in the wavelength of maximum emission intensity between triboluminescence and photoluminescence spectra is observed for the 4f65d-4f7 transition of Eu2+, whereas the peak positions and the relative intensities of emission lines in triboluminescence and photoluminescence spectra are almost the same as each other for the 4f-4f transitions of Th3+ and Dy3+. This is because the 5d levels, which are more significantly affected by ligand fields than the 4f levels, contribute to the transition of Eu2+. It is thought that the difference in local environment around the Eu2+ between on the fractured surface and within the bulk brings about the discrepancy between triboluminescence and photoluminescence spectra

Measurements of Faraday and Mössbauer effects have been performed at room temperature for alkali silicate glasses containing a large amount of Eu2+ ions to examine the relation between local structure and magnitude of Verdet constant. The Mössbauer spectra indicate that about 80% of europium ions are present as a divalent state. The effective transition wavelength and effective transition probability for the 4f7 → 4f65d transition of Eu2+, which causes the Faraday effect, are derived from the wavelength dependence of Verdet constant. Both effective transition wavelength and effective transition probability are large compared with borate glasses, leading to the large magnitude of Verdet constant of the alkali silicate glasses. The variation of effective transition wavelength with glass composition is connected with the change of 6s-electron density of Eu2+ evaluated from the Mössbauer spectroscopy.

Optical second harmonic generation has been observed in transparent tellurite glass-ceramics of Ba0-TiO2-TeO2 system. BaTiO3 and unidentified crystalline phase precipitate from 15BaO·15TiO2·7OTeO2 glass. The temperature of maximum rate of nucleation for these crystalline phases is estimated to be 380°C. The BaTiO3 crystal precipitated is a cubic phase with lattice parameter of 0.4045 nm, which is slightly larger than the value reported in the JCPDS cards. The optical second harmonic intensity of the present transparent tellurite glass-ceramics is comparable to the intensity of poled tellurite glasses although the BaTiO3 phase precipitated is cubic and the crystal face is randomly oriented in the glass-ceramics. For instance, the second harmonic intensity of the present transparent tellurite glass-ceramics is about twice as large as that of 20WO3·80TeO2 glass poled at 280°C under the external electric field of 3 kV, the second-order nonlinear coefficient, d33, of which is 0.10 pm/V.