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In this work, we investigated the effect of doping zinc ions onto nickel ferrite upon the structure, morphology, and magnetic properties of Ni1 − xZnxFe2O4 ferrite nanoparticles (x = 0, 0.25, and 0.75) prepared via co-precipitation method. X-ray diffraction analysis showed the presence of the most intense peak corresponding to the (311) crystallographic orientation of NiFe2O4 cubic spinel phase, and the crystallite size obtained from Scherrer formula increased from 6.8 to 11.2 nm when the Zn concentration increases from x = 0 to x = 0.75. Fourier transform infrared spectroscopy analysis confirmed the presence of a prominent band associated to the vibrations of metal ions, as a feature of spinel ferrite phase formation, observing that their band positions were very sensitive to Zn doping concentration. Transmission electron microscopy studies allowed to determinate that for all Zn concentrations, the particle sizes are around 15 nm. The magnetic properties were studied by using the vibrating sample magnetometer at room temperature. The results reveal superparamagnetic behavior determined by the shape of the hysteresis loop, presenting decreased coercive magnetic field and increased saturation magnetization, with increased zinc concentration. Additionally, from field cooling and zero field cooling curves, we can observe the typical behavior of the blocking process assembly of superparamagnetic nanoparticles. Alternate current susceptibility measurements show that the blocking temperature is frequency dependent and shifts toward higher temperatures by increasing the frequency, a characteristic of superparamagnetic, and glassy systems. Furthermore, τ0, related to the jump attempt frequency of the magnetic moment of the nanoparticle between the opposite directions of the magnetization easy axis, is in the range of 2 × 10−10 and 7 × 10−13 s for the three different Zn concentrations, which agrees with characteristic of non-interacting superparamagnetic systems. [ABSTRACT FROM AUTHOR]

Semiconductor heterojunction of β-Bi2O3-TiO2/ITO thin films was prepared by aqueous sol-gel and their photoelectrochemical and photoelectrocatalytic properties were evaluated on the oxidation of salicylic acid. The β-Bi2O3 sol precursor properties were characterized by DLS, SEM, and X-ray diffraction. The composition and morphology of the films were characterized by SEM-EDS. The photoelectrochemical characterization was performed by linear sweep voltammetry with chopped light irradiation and photocurrent measurements. The photoelectrocatalytic activity of the films under UV-Vis and visible light irradiation was conducted on the oxidation of salicylic acid. Results show that the films are composed of a TiO2 layer with Bi2O3 particles dispersed throughout the surface. X-ray diffraction results confirm that the Bi2O3 obtained from the sol precursor prepared corresponds to β-tetragonal phase. The linear sweep voltammetry shows that the β-Bi2O3-TiO2/ITO films have a higher photocurrent in the anodic region than TiO2/ITO films used as reference. The photoelectrocatalytic activity of the β-Bi2O3-TiO2/ITO films on the oxidation of salicylic acid under visible light irradiation was higher than TiO2/ITO films. The results show that the β-Bi2O3-TiO2/ITO films are active under visible light and can be used in photoelectrochemical cells. [ABSTRACT FROM AUTHOR]

Focuses on a study which investigated visible and near infrared cathodoluminescence of Bi[sub2]Sr[sub2]CaCu[sub2]O[subx] and YBa[sub2]Cu[sub3]O[sub7-x] films in the scanning electron microscope. Capability of the cathodoluminescence technique; Use of luminescence techniques; Result of the complex character of the blue emission.

In this work, we report magnetoelectric coefficient measurements in BiFeO3 (BFO) compounds using dynamic lock-in technique to evidence magnetoelectric coupling behavior. The response of the magnetoelectric coefficient shows rapid increase from low frequencies (0.1 kHz) to around 5 kHz, reaching a maximum, and then decreasing monotonously to 100 kHz. For a constant frequency at 7 kHz, the maximum magnetoelectric coefficient was close to 7 mV/cm Oe, obtained at a bias magnetic field of H=120 Oe. Thus, we demonstrated the feasibility of this technique for characterizing multiferroic materials. [ABSTRACT FROM AUTHOR]

We have grown Yba[SUB2]Cu[SUB3]O[SUB7-δ] (40 nm)/La[SUB1/3]Ca[SUB2/3]MnO[SUB3] (2 nm)/La[SUB2/3]Ca[SUB1/3]MnO[SUB3] (30 nm) junctions for quasiparticle-injection measurements. Ferromagnetic (F), antiferromagnetic (AF), and superconducting (S) thin films were sequentially grown "in situ" using a dc-sputtering technique at 850 °C in pure oxygen at pressures around 3.5 mbar. The temperature dependence of the resistivity of the junction, without any current injection, presented coexistence between magnetism and superconductivity with a metallic insulating transition at 186 K, and zero resistance at 52 K. When current was injected from the F layer into the S layer, superconductivity suppression was obtained at temperatures below 52 K; furthermore, small values of current injection were necessary to change the electrical behavior up to the critical temperature. A negative current gain (G) has been observed and described by the relation G ∝ ατ[SUBeff], where τ[SUBeff] is the relaxation time of the quasiparticle. The use of an AF layer as an insulating barrier is also discussed. [ABSTRACT FROM AUTHOR]