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In this paper, we present the results of the study of the effect of residual La on crystal structure, magnetic properties of La1+dFe11.05Si1.95 (d = 0.00; 0.03; 0.06 and 0.09) compounds. The analysis of X-ray diffractions showed that when the La content increases to 9%, the structure still remains cubic in a typical NaZn13 arrangement with unchanged lattice constant (about 0.5%). All compounds exhibit ferromagnetic - paramagnetic phase transitions. The Curie temperature TC increases slightly from 235 to 245 K.

TiO 2 powders doped with different amounts of Cr 3+ ions (from 0 to 10 mol%) have been prepared by hydrothermal technique. TiO 2 :Cr 3+ powders were characterized by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, diffuse reflection, absorption, photoluminescence and photoluminescence excitation spectra. The results showed that the Cr 3+ dopant concentrations did not affect on the lattice constants of TiO 2 crystal, but affected on shift and broadening of the Raman modes for both anatase and rutile phases. The band gap of both the anatase and rutile TiO 2 host lattice was strongly decreased with increasing Cr 3+ dopant concentration. The photoluminescence spectra of TiO 2 :Cr 3+ anatase phase exhibited a weak narrow peak (the so-called R-line) at 698 nm, meanwhile those of TiO 2 :Cr 3+ rutile phase consisted of a very intense narrow zero-phonon R-line at 695 nm assigned to the 2 E( 2 G) → 4 A 2 ( 4 F) transition of Cr 3+ ions in strong octahedral field and its phonon-sidebands. In particular, in the PL spectrum of TiO 2 :Cr 3+ rutile phase is also observed an abroad emission band centered at 813 nm assigned to the 4 T 2 ( 4 F) → 4 A 2 ( 4 F) transition of ions Cr 3+ in weak octahedral field.

The saturated magnetization in 20% substituted La0.8R0.2(Fe0.88Si0.12)13 (R = Sm, Tb) magneto-caloric alloys is discussed in this work. The measurements were taken up to 70 kOe (7 Tesla) to detect the saturation of magnetic moments. As reported recently [Mat. Trans. 59(7) (2018) 1068], these compounds show a large variation of magnetic entropies at low field variation (~ 1.5 T), which associate with the large relative cooling efficiency (RCP) of 52 (for Tb-doped) and 102 J/kg (for Sm-doped) even at low effective DH of ~ 15 kOe. We re-detected the effective range of field variation DH and recognized that the effective DH ~ 5 kOe which is much lower than the value of other magneto-caloric compounds and is excellent for application of Sm-doped compound in modern cooling devices. Keywords: Magnetic, alloys, LaFe13, phase transition, rare-earth.

Control of the conditions that affect the formation of the anatase and rutile phases of TiO2 is of considerable interest. The aim of this work was to study the effect of Fe doping on the anatase to rutile transformation for the TiO2:Fe3+ samples not undergo annealing at high temperatures. In the hope of increasing photocatalysis efficiency, the decrease of TiO2 band-gap energy caused by Fe doping was studied. The Fe3+-doped TiO2 (TiO2:Fe3+) nanoparticles with dopant contents ranging from 0 to 14.54 at% have been synthesized by hydrothermal method. Different techniques such as transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman scattering, diffuse reflection and photoluminescense spectroscopy were used to characterize the synthesized nanoparticles. The results showed that the increase of Fe3+ dopant content up to 9.29 at% leaded to the anatase to rutile phase transformation. The Fe-doping resulted in the shifting and broadening of the Raman modes, and the red shift of the absorption edge of the TiO2:Fe3+ nanoparticles as well. The band gap energy decreased from 3.57 to 3.06 eV for the direct and from 3.21 to 2.14 eV for indirect transitions with increasing Fe3+-doping concentration from 0 to 14.54 at%. In addition, the presence of Fe3+ dopant affected the photoluminescence spectra of the nanoparticles.

Department of Physics and Research Institute for Convergence of Basic Science,Hanyang University, Seoul 133-791, Korea(Received March 25, 2015 : revised June 1, 2015 : accepted June 26, 2015)Transmission characteristics of long-period fiber gratings (LPFGs) fabricated by periodically etching a conventional single-mode fiber (SMF) are investigated. After coating the SMF with photoresist, the cladding of the SMF is symmetrically and periodically removed by using a wet etching technique resulting in the formation of the LPFG. Tensile strain reinforces the coupling strength between the core and the cladding mode based on the photoelastic effect. The extinction ratio of the SMF-based LPFG at a wavelength of 1550.8 nm is measured to be -15.1 dB when the applied strain is 600 µe. The ascent of ambient index shifts the resonant wavelength to shorter wavelength because of the increase of the effective refractive index of the cladding mode. The extinction ratio is diminished by increase in the ambient index because of the induction of the optical attenuation of the cladding mode. The transmission characteristics of the proposed LPFG with variations in torsion are also measured. The photoelastic effect based on torsion changes the extinction ratio and the resonant wavelength of the proposed SMF-based LPFG. The polarization-dependent loss of the LPFG is also increased by torsion because of the torsion-induced birefringence. The polarization-dependent loss of the LPFG at torsion of 8.5 rad/m is measured to be 3.9 dB.Keywords : Long-period fiber gratings, Fiber-optic sensors, Photoelastic effectOCIS codes : (060.0060) Fiber optics and optical communications; (060.2370) Fiber optics sensors; (050.2770) Gratings

Magnetic and magnetocaloric properties in Ni50Mn50−xSnx alloys with wide range of the Sn-concentration (x=0–40) were investigated. The alloys were prepared by arc-melting and subsequently annealing at 850 °C for 4 h. The X-ray diffraction analyses manifest the formation of the crystalline phases (Ni2MnSn, NiMn, Ni3Sn2, Mn3Sn, and MnSn2) in the alloys with various compositions and fabrication conditions. With increasing x, the saturation magnetization first increases from near zero (at x=10) to above 40 emu/g (at x=20) and then decreases to below 10 emu/g (at x=40) for both the as-melted and annealed cases. The martensitic–austenitic transition was observed in the alloys with a narrow range of x (13–15). The magnetic transitions in the alloy can be controlled by changing Sn-concentration. The alloy reveals both the positive and negative entropy changes with quite large magnitude (∆Sm>1 J/kg K with ∆H=12 kOe) with appropriate compositions and annealing conditions.

Fe90−x Ni x Zr10 (x = 0, 5, 10, 15, 20 and 25) ribbons with various thicknesses were prepared by using a melt-spinning technique. The Curie temperature, T C , of the alloys dramatically decreased from ∼960 K to room temperature at high quenching rates. When the alloys had an amorphous structure, their T C strongly depended on the Ni concentration. The maximum entropy change, |ΔS m | max , with ΔH = 12 kOe, of the alloys was around 1 J·kg−1K−1 at room temperature. On the other hand, the full width at half maximum the entropy-change peak was quite large, ∼ 85 K, which was suitable for applications in magnetic refrigerators at room temperature.

We report the errors in the evaluation of the surface plasmon resonance of gold nanorods by three classical approaches: the Gans model, the Discrete Dipole Approximation and the Surface Integral method. Using these methods, which are based on the propagation of an electromagnetic wave through a composite medium with different refractive indices, might result in an inaccurate prediction of absorption maxima. For test samples of nanorods prepared by a seed-mediated method, whose homogeneity and quality were also fully demonstrated in this study, the mismatches in the wavelengths of absorption maxima $$ \left| {\varDelta {\lambda_{\max }}} \right| $$ between experimental and theoretical data were observed to be greater than 50 nm. In general, the observed surface plasmon resonances exhibit two distinctive bands corresponding to the transverse and longitudinal modes. The weak transverse mode was located in the region from 510 to 518 nm and varied slightly with the aspect ratio of the rods. In contrast, the longitudinal mode showed a strong dependence on aspect ratio and ranged from 658 to 768 nm. We demonstrated that the mismatches may be sufficiently reduced if the interdependence between these two modes is taken into account.

Measurement of the Charm Production in γγ Interactions at LEP PDF-Abstract. PDF-Abstract.

The inclusive production of D*± mesons in two-photon collisions is measured with the ALEPH detector at e+e centre-of-mass energies from 183 GeV to 209 GeV. A total of 360 ± 27 D*± meson events are observed from an integrated luminosity of 699 pb -1 . Contributions from direct and singleresolved processes are separated using the ratio of the transverse momentum pt D*± of the D*± to the visible invariant mass Wvis of the event. Differential cross sections of D*± production as functions of pt D*± and the pseudorapidity |D*±| are measured in the range 2 GeV/c < pt D*± < 12 GeV/c and |D*±| < 1.5. They are compared to next-to-leading order (NLO) perturbative QCD calculations. The extrapolation of the integrated visible D*± cross section to the total charm cross section, based on the PYTHIA Monte Carlo program, yields (e+e→ e+ecc _ ) < s >=197 GeV = 731 ± 74stat ± 47syst ± 157extr pb.