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The crystal structures, magnetic, and dielectric properties for the ordered double perovskites LnPbCoSbO6 (Ln = La, Pr, Nd) have been investigated. The crystal structure has been solved by Rietveld refinements of X-ray diffraction data in the monoclinic space group P21/n (No. 14). The Co2+ and Sb5+ ions are almost fully ordered over the B-site, and the octahedral framework displays significant tilting distortion according to the Glazer's tilt system a-a-c+. As the result of lanthanide contraction from La3+ to Nd3+, the B-site sublattice distortions become stronger accompanying with the reduction of the tolerance factor and coordination number. The magnetization measurements show an antiferromagnetic ordering with large effective magnetic moments (μeff) suggesting that the orbital component is significant. The maximum values of isothermal magnetization increase with the decrease in radii of rare earth ions, which is attributed to the weakening of antiferromagnetic interaction via Co2+-O-Sb5+-O-Co2+ paths. The dielectric constants present frequency dependence and monotonically decrease with the ionic radii reduction from La3+ to Nd3+ due to the suppression of electron transfer. These results indicate that the magnetic and dielectric properties can be tuned by controlling the degree of lattice distortion, which is realized by introducing different Ln3+ ions at the A-site. [ABSTRACT FROM AUTHOR]

α- and β-FeSe thin films were grown by metal organic chemical vapor deposition. Compared to the other parameters, the growth temperature shows decisive influence on the phase transition of the FeSe samples. In temperature-dependent electrical measurements, n-type to p-type reversion was observed for both the α- or and β-FeSe samples. Furthermore, the p-type character of the films becomes more and more obvious with increasing the Se/Fe atomic ratio in the samples. Ferromagnetism was observed in the α-FeSe films although which is not supported by calculation on density of states. The ferromagnetic character shows significant dependence on Se/Fe atomic ratio in the films and was attributed to the Fe vacancies or Fe clusters in the α-FeSe thin films. The magnetic domain and hysteresis loop of the β-FeSe thin films are also studied. [ABSTRACT FROM AUTHOR]

Deals with a study which investigated the influence of oxygen pressure on epitaxial quality of lanthanum...strontium...AlTa Oxygen... thin films deposited by laser ablation on different substrates. Experimental details; Results and discussion; Conclusion.

Presents information on a study which described the 2a[sub0]x2b[sub0]xc[sub0] superstructure in bi-based cuprate superconductors using electron diffraction. Characteristics of the superconductors; Experimental details; Results and discussion; Conclusions.

The optical and electrical properties of FeSe thin films are studied by both optical absorption and Hall measurements, which suggest that ferromagnetic FeSe is a metal instead of a semiconductor. No absorption gap is observed in the whole spectrum range from far infrared to ultraviolet. Temperature dependent transport measurement indicates that FeSe has a resistivity about 10-3 Ω cm. It is also found that there is a transition from n-type conductivity at low temperatures to p-type conductivity at higher temperatures in FeSe, which is attributed to the two-carrier transport nature and the thermal activation of localized carriers in the thin film. [ABSTRACT FROM AUTHOR]

Granular thin film samples composed of Fe clusters embedded in CdFeS were prepared with using low pressure metal organic chemical vapor deposition. Temperature dependence of the resistivity of the granular film follows well the relationship for the tunneling transport between the iron granules. A large negative magnetoresistance of about 2.2% at 0.1 T was observed at room temperature due to the presence of Fe clusters. The hysteresis behavior observed in the magnetoresistance corresponded exactly to those of the hysteresis loop in the magnetization measurement, which evidently showed the correlation between the magnetoresistance and global magnetization in the sample. [ABSTRACT FROM AUTHOR]

Cd1-xFexS thin films with different Fe contents were grown on c-plane sapphire by low-pressure metal organic chemical vapor deposition. The resistivity of the thin films was found to increase with the addition of more Fe contents into the Cd1-xFexS thin films by elevating the growth temperature, which was attributed to the ionization of holes from trivalent Fe ions. High density Fe doping eventually reversed the conductivity of Cd1-xFexS thin film from n to p type. With increasing Fe content, the band-to-band transition at 2.5 eV was suppressed while the emission from the donor-acceptor pairs at 2.0–2.4 eV finally dominated the photoluminescence spectra. [ABSTRACT FROM AUTHOR]

Uniform ZnSe nanowires are observed on the ablation crater on ZnSe crystal surface irradiated by femtosecond lasers in air, while other parts of the sample surface are not polluted. The nanowire growth rate is about 5 μm/s, it is higher than that fabricated by chemical vapor deposition method by a factor of 104. The nanowire length and diameter can be controlled by varying laser pulse energy and pulse number. The formation mechanism is studied and found to be self-catalyzed vapor-liquid-solid process. [ABSTRACT FROM AUTHOR]

Short-range structure of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass prepared by shock-wave treatment was investigated by x-ray diffraction using synchrotron radiation with a wavelength of 0.112 71 Å. The radial distribution function was obtained from S(Q) with a large Q value up to 20 Å-1. The oscillation in S(Q) of the glass definitely persists up to Q∼14 Å-1. The shoulder on the high Q side of the second peak is observed in the bulk glass. It is found that the glass has higher coordination numbers in the range of r∼2.4–5.6 Å and lower numbers in the range of r∼5.6–9.5 Å than those for a water-quenched glass while the shell distances are similar in both glasses prepared by shock-wave and water-quenching methods. In the shock-waved glass, atomic configurations in the first, fourth, or fifth coordination shells are modified, i.e., atoms are packed denser in the first two coordination shells and less (or more free volume) in the third and fourth coordination shells as compared to those for the water-quenched glass. This atomic configuration for shock-waved glass might have different physical properties. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

(Hg[sub 1-x]Re[sub x])Ba[sub 2]CaCu[sub 2]O[sub y] (xapprox. 0.1) thin films have been prepared ex situ on LaAlO[sub 3] substrates by a two-step process in which an HgO/Re[sub 0.1]Ba[sub 2]CaCu[sub 2]O[sub y] multilayer precursor film is annealed in a quartz tube using an unreacted monoxide pellet containing HgO as an Hg vapor source. By varying the composition of the monoxide pellet, the film orientation can be changed from c-axis to the predominantly a-axis one. The a-axis growth of the grains directly on the substrate is confirmed by x-ray diffraction and transmission electron microscopic observation, although the grains are twinned with 90° orientation. The a-axis films exhibit a T[sub c] onset and T[sub c] zero of approximately 110–127 and 55 K, respectively, suggesting substantial influence of weak links at the grain boundaries on their transport properties. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]