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Abstract: TiO2/Co thin films were prepared on glass substrates under thermal non-equilibrium condition by alternately sputtering very thin TiO2 and Co layers for 60 periods. Microstructure and composition analyses by X-ray diffraction, transmission electron microscopy, X-ray photoemission spectroscopy and electron energy-loss spectroscopy indicated that the Co element was incorporated into TiO2 to form the Ti1− x Co x O2 magnetic semiconductors. The obvious Kerr rotations in the samples were observed, and the relation between the Kerr rotation and Co concentration was discussed. [Copyright &y& Elsevier]

Abstract: The resonant modes in a quantum well (QW) structure composed of three slabs of two dimensional (2D) photonic crystals with different lattice constants are analyzed with plane-wave-based transfer matrix method (TMM). It is found that the energy band of the well slab submerged into the band gap of barrier slab is discretized into quantized modes and the number of the resonant modes changes with the well slab thickness. A model structure of asymmetrical photonic QW consisting of two slabs of 2D photonic crystals with different lattice constants and one uniform dielectric slab in between is proposed and the resonant modes in it are investigated with the same method. A useful numerical simulation method for theoretical discussion as well as for practical application about photonic QW structure of photonic crystals with different lattice constants is proposed. [Copyright &y& Elsevier]

We propose a defect-complex model to clarify the origin of ferromagnetism in Co-doped ZnO magnetic semiconductors, based on first-principles calculations. The spin-polarized defect states of oxygen vacancy (VO) induced by the charge-transfer process are essential to the ferromagnetism. Depending on the charge state of VO and carrier concentration, (VO 2+ +zinc interstitial) and (VO 0 +zinc vacancy) defect complexes are predicted to control the ferromagnetic exchange interaction between the Co ions for insulating and conductive samples, respectively. [ABSTRACT FROM AUTHOR]

Abstract: A novel approach was developed to calculate temperature-dependent Seebeck coefficient of heavily doped systems. The electronic density of states (DOS) and Fermi energy were determined and then, using these two parameters, the Seebeck coefficient was calculated by using Boltzmann transport theory. This approach is applied to heavily La-doped SrTiO3. The calculated Seebeck coefficient agrees well with the experimental data. By analyzing the results, it was shown that Seebeck coefficient is greatly affected by the asymmetry of DOS with respect to Fermi energy. [Copyright &y& Elsevier]

Abstract: Amorphous GaN (a-GaN) films on Si (111) substrates have been deposited by RF magnetron sputtering with GaN powder target. The growth process from amorphous GaN to polycrystalline GaN is studied by XRD, SEM, PL and Raman. XRD data mean that annealing under flowing ammonia at 850–950°C for 10min converts a-GaN into polycrystalline GaN (p-GaN). The growth mechanism can be mostly reaction process through N3− in amorphous GaN replaced by N3− of NH3. Annealing at 1000°C, the appearance of GaN nanowires can be understood based on the vapor–liquid–solid (VLS) mechanism. In addition, XRD, PL and Raman measurement results indicate that the quality of GaN films increases with increasing temperature. The tensile stress in the films obtained at 1000°C is attributable to the expansion mismatch between GaN and Si, with the gallium in the film playing a negligible role. [Copyright &y& Elsevier]

Abstract: TiO2:Co thin films of high Co concentration were investigated by the high resolution transmission electron microscopy, physical property measurement system and energy dispersive X-ray. The as-deposited films are amorphous magnetic semiconductors and we did not find any Co metal particles in them. The electronic transport process in the low-temperature range below 80K could be described by the spin-dependent variable-range-hopping process. However, after the samples were annealed at 300°C, large amounts of Co metal particles were observed to connect each other and the films show a metallic behavior. The origin of ferromagnetism of the thin films is also discussed. [Copyright &y& Elsevier]

Abstract: Structural, magnetic, electrical, and magnetotransport properties have been carried out on the Ag-added La0.67Ba0.33MnO3/(TiO2)0.035 (LBT) (abbreviated by LBT/Ag x ,) composites. Ag addition has little influence on the magnetization or Curie temperature (T C), but decreases the resistivity (ρ) and sharps the ρ peak evidently. The ρ in the ferromagnetic (FM) metallic regime is proportional to T 2, reflecting that the conductive mechanism mainly arises from the electron–electron scattering. In the paramagnetic (PM) insulating region, the ρ data fit well to the self-trapped small polaron hopping model. The ρ–T curves for x =0.27 and 0.30 samples fit well with the phenomenological percolation approach, which is based on the phases segregation of ferromagnetic metallic clusters and paramagnetic insulating regions. These excellent agreements highlight the dominant intrinsic behavior of LBT. In addition, from the magnetotransport measurements, a large magnetoresistance (MR) ratio up to 41% was obtained at 280K, and 10kOe for x =0.27 sample. The good fits between the field dependence of MR and Brillouin function indicate that the MR behavior in the Ag-added LBT is induced by the spin-dependent hopping of the electrons among the spin clusters, and which is related to the increase and growth of the FM spin clusters. [Copyright &y& Elsevier]

Abstract: We have prepared a series of polycrystalline manganites with the nominal compositions, La0.67Ba0.33Mn0.88Cr0.12O3/Ag x (LBMCO/Ag x ) (x is the mole fraction) with , 0.05, 0.1, 0.15, 0.2, 0.23, 0.27, 0.3, 0.35. The X-ray diffraction patterns show that the samples with are two-phase composites. The Ag addition in LBMCO improves the properties of grain surfaces/boundaries and reduces the resistivity of the composites. For sample, a minimum resistivity is obtained and a maximum room temperature magnetoresistance up to −54.5% was observed at 288K, 1T field. The room temperature T C and the reduced resistivity are responsible for the enhancement of room temperature MR. [Copyright &y& Elsevier]

Abstract: The giant magnetoimpedance (GMI) effects in radio frequency sputtered FeCuNbSiB films with a dc magnetic field applied in the process of deposition are presented, and the relation between annealing temperature and GMI ratio is investigated. The results show that 300 °C is the optimum annealing temperature, at which the GMI ratios reach the maximum values of about 38% and 27% in longitudinal and transverse dc magnetic fields, respectively, at a frequency of 13 MHz. The longitudinal magnetic responses of GMI ratios show very sharp peaks around the transverse anisotropy field, and the sensitivity can reach a value larger than 47.5%/kA/m in the field range 0.4∼6 kA/m, at 13 MHz. The frequency dependencies of the magnetoresistance and magnetoreactance indicate that at lower frequencies, the giant magnetoinductance effect is dominant, while at higher frequencies, skin effect becomes important, and the GMI effect is determined by the change of both the resistance and reactance components. [Copyright &y& Elsevier]

Abstract: The electrical and magnetoresistant properties of La0.67(Ca0.65Ba0.35)0.33MnO3/Ag x (abbreviated by LCBMO/Ag x ) have been studied. The results show that Ag addition causes a decrease of resistivity dramatically and especially induces a large enhancement of room temperature magnetoresistance (MR). The room temperature MR ratio for x=0.27 sample in 10kOe magnetic field is 41%, almost 20 times larger than that for x=0 sample. This enhancement is related to that the Curie temperature (T c) of the sample is near room temperature, as well as the significant reduction of resistivity. The good fits of experimental results for x=0.27 sample to Brillouin function indicate that the MR behavior in the Ag added LCBMO is induced by the spin-dependent hopping of the electrons between the spin clusters, which is an intrinsic property of the CMR materials. [Copyright &y& Elsevier]

Abstract: Lattice vibration in one-dimensional copolymer chains was studied in the framework of a tight-binding model including the interfacial coupling between homopolymer segments. The vibration density of states was obtained numerically and the characteristic of the vibration modes was recognized. It was found that there exist two types of modes, confined and hybridized. Interface modes might appear at a strong interfacial interaction. The characteristic of the organic quantum well or superlattice of a copolymer chain was discussed from the point of the lattice vibration. [Copyright &y& Elsevier]

Enhancements of the low-field (LFMR) and high-field magnetoresistance (HFMR) were observed in the manganite system prepared by doping Nb2O5 into La0.67Sr0.33MnO3 powders. The maximum MR ratios at 77 K with H=1 T and 1 kOe are 30% and 20% for the 0.07 molar ratio doped sample, which are 1.7 times and 1.6 times as large as that for LSMO, respectively. An MR effect up to 6.5% was also found for the sample with x=0.03 at room temperature (RT). The spin-dependent tunneling and scattering at the interfaces of grain boundaries are responsible for the LFMR while the HFMR originates from a noncollinear spin structure in the surface layer. With increasing x, the Curie temperature (TC) decreases monotonically from 364 to 154 K while the temperature TP related to the peak resistivity decreases firstly to a minimum of 204 K (x=0.06) and then rises up to 240 K (x=0.1). There is a maximum resistivity ρ for the sample with x=0.06, which is higher than that for LSMO by five orders of magnitude. It is due to the enhancement of spin-dependent and independent scattering and tunneling effects on the interfaces of grain boundaries and inside the grains. [Copyright &y& Elsevier]

La0.67Ca0.33MnO3 (LCMO) fine powder was prepared by a sol–gel procedure. The effects of Ti addition in LCMO on the magnetic, transport and magnetoresistive (MR) properties have been studied systematically. With increasing Ti addition, the magnetization and Curie temperature for the samples decrease monotonously, and the resistivity increases dramatically. The MR effect increases first and then decreases after a maximum MR ratio is reached. When the amount of Ti addition is 5.5% (molar ratio), a maximum MR ratio as large as 500% in 10 kOe at 120 K was obtained, which is 25 times larger than that obtained by the undoped LCMO. The effect of Ti addition is to introduce local magnetic inhomogeneity and inducing spin clusters in the material. Fitting the experimental results to the Brillouin function proposed by Wagner et al. indicates that a possible explanation for the MR behaviour in the Ti-doped LCMO is the formation of spin clusters. [Copyright &y& Elsevier]