Measurement of Fluctuation-induced Diamagnetism in BSCCO-2212 single crystals using Magneto-optics

Fluctuation induced diamagnetism in BSCCO single crystals with different doping levels (i.e., different oxygen stoichiometry) was measured using magneto-optics (MO) in a wide frequency range up to several MHz. A shift in Tc onset, measured by MO, of up to 6 K towards higher temperatures was observed at high frequencies in those samples which are far from the optimally doped condition. An explanation of the observed effect in terms of the phase fluctuations of the superconducting order parameter is proposed.Comment: 13 pages, 3 figure

The synthesis of nanocrystalline YIG in an ammonium nitrate melt

Yttrium iron garnet particles were synthesized in two different ways: first, in an ammonium nitrate melt (ANM) and second, via a solid-state reaction (SSR) route. The structural and magnetic properties of the samples were compared using XRD, SEM and dc magnetization measurements. It was observed for the ANM technique that the phase formation of YIG starts at 1000 degrees C and then develops with increasing temperature and sintering times. The saturation magnetization, M(s), increases sharply with increasing annealing temperature and then saturates at around 23 emu g(-1) above 1100 degrees C, while the coercivity decreases due to the increasing particle size. An almost single-phase sample was obtained through ANM route by annealing for 2 h at 1300 degrees C, after which the YIG fraction in the SSR sample was only 0.34, with M(s) = 7.08 emu g(-1). The average particle sizes of the ANM samples were calculated using experimentally determined M(s) values. It appeared that they vary from the sub-micron to the micron range, depending on the sintering temperature, and this coincides with the values determined from the SEM micrographs. These samples have homogeneous structures, small grains, good magnetic properties, and do not contain massive agglomerates. Therefore, the synthesis of YIG via the ANM technique represents another alternative to the SSR route

Properties of YBCO superconductors prepared by ammonium nitrate melt and solid-state reaction methods

Ceramic YBCO superconductors were prepared by: (1) ammonium nitrate melt, (2) solid-state reaction methods and the properties of the samples obtained were compared. Under the same annealing conditions single phase YBCO was synthesized at a lower temperature by the former method. Moreover, at 900 degrees C Y-123 phase and the initially adjusted Y-211 additive could be formed using ammonium nitrate melt, but not with the solid-state method which leads Y-123 at a higher temperature (950 degrees C) without Y-211 additive. The samples prepared with ammonium nitrate melt technique have smaller grains, more grain boundaries and weak links causing low J(c), and wide superconducting transition temperature. Superconductors produced by this technique may be suitable for applications like magnetic field sensors that require small grains and reversible magnetization

Phase Identification of La-Doped Hard Magnetic Barium Ferrite Using Artificial Neural Network

A model based on an artificial neural network (ANN) was designed for the simulation and estimation of 2 theta and intensity values obtained by X-Ray Diffraction (XRD) of pure and La-doped barium ferrite powders which have been synthesized in ammonium nitrate melt. Its performance is evaluated by the influences of different La content, sintering temperature, Fe/Ba ratio, and washed in HCl (or not washed in HCl) samples. The XRD patterns of samples estimated by the ANN agree well with the experimental values, indicating that the model is reliable and adequate

Modeling of Magnetic Properties of Nanocrystalline La-doped Barium Hexaferrite

In this paper an artificial neural network (ANN) has been developed to compute the magnetization of the pure and La-doped barium ferrite powders synthesized in ammonium nitrate melt. The input parameters were: the Fe/Ba ratio, La content, sintering temperature, HCl washing and applied magnetic field. A total of 8284 input data set from currently measured 35 different samples with different Fe/Ba ratios, La contents and washed or not washed in HCl were available. These data were used in the training set for the multilayer perceptron (MLP) neural network trained by Levenberg-Marquardt learning algorithm. The hyperbolic tangent and sigmoid transfer functions were used in the hidden layer and output layer, respectively. The correlation coefficients for the magnetization were found to be 0.9999 after the network was trained

Optoelectronic design parameters of interferometric fiber optic gyroscope with LiNbO₃ having north finder capability and earth rotation rate measurement<b></b>

375-384North finder capability gyroscopes supply the reference north azimuth information to the relevant base system. This paper covers the design details of both optical and electronic components of an open-loop Interferometric Fiber Optic Gyroscope (IFOG) with integrated-optic phase modulator LiNbO3 and the measurement results of earth rotation rate carried out by means of the designed north finder IFOG with LiNbO3 modulator in laboratory plane together. Scale factor model function is derived for the open-loop IFOG with LiNbO3. Additionally, bias stability and the temperature dependence of the bias stability for the north finder IFOG have been studied in the temperature range 23°-42°C

Triethylene Glycol Stabilized CoFe2O4 Nanoparticles

We report on the synthesis and detailed composition, thermal, micro-structural, ac-dc conductivity performance and dielectric permittivity characterization of triethylene glycol (TREG) stabilized CoFe2O4 nanoparticles synthesized by polyol method. XRD analysis confirmed the inorganic phase as CoFe2O4 with high phase purity. Microstructure analysis with TEM revealed well separated, spherical nanoparticles in the order of 6 nm, which is also confirmed by X-ray line profile fitting. FT-IR analysis confirms that TREG is successfully coated on the surface of nanoparticles. Overall conductivity of nanocomposite is approximately two magnitudes lower than that of TREG with increase in temperature. The ac conductivity showed a temperature dependent behavior at low frequencies and temperature independent behavior at high frequencies which is an indication of ionic conductivity. The dc conductivity of the nanocomposites and pure TREG are found to obey the Arrhenius plot with dc activation energies of 0.258 eV and 0.132 eV, respectively. Analysis of dielectric permittivity functions suggests that ionic and polymer segmental motions are strongly coupled in the nanocomposite. TREG stabilized CoFe2O4 nanoparticles has lower epsilon' and epsilon '' than that of pure TREG due to the doping of cobalt. As the temperature increases, the frequency at which (epsilon '') reaches a maximum shifted towards higher frequencies. On the other hand, the activation energy of TREG for relaxation process was found to be 0.952 eV which indicates the predominance of electronic conduction due to the chemical nature of TREG. Contrarily, no maximum peak of tan delta was observed for the nanocomposite due to the being out of temperature and frequency range applied in the study

Enhancement in the high-T-c phase of BSCCO superconductors by Nb addition

WOS: 000247046400011Pure and Nb2O5 added Bi1.6Pb0.4Nbx Sr2Ca2Cu3O delta superconductors ( x varies up to 0.30) were synthesized by the solid state reaction method. Structural and superconducting properties of the samples were investigated. The fraction of the high-T-c phase ( 2223) increases with Nb addition up to x = 0.10, for which a nearly single 2223 phase was obtained. The critical temperature of the samples increases from 96 to 104 K with doping up to x = 0.20 and a further increase in Nb decreases the Tc sharply. Similarly, there is a considerable enhancement in the critical current density ( jc) of the samples in the same doping range. Both AC susceptibility and transport measurements showed that the optimum Nb concentration is x = 0.20. The out- of- phase component of the AC susceptibility measurements showed that inter- grain coupling was enhanced up to the same doping level. Nb additions above x = 0.30 decrease the fraction of the high- Tc phase and degrade the superconducting properties. Present measurements indicate that x = 0.20 is the optimum Nb concentration in the BSCCO superconductor to enhance phase purity, inter- grain coupling and superconducting parameters ( Tc and j(c))

Impact of sonication time in nanoparticle synthesis on the nutrition and growth of wheat (Triticum aestivum L.) plant

Nanotechnology in agricultural applications is promising in improving plant nutrition and yield, pest control, and gene delivery. However, the method to synthesize nanoparticles or nanocomposites (NCs) can play a crucial role in determining the characteristics of NCs, such as size and morphology, which may be critical factors affecting plant nutrition and NCs` potential toxicity. This study elucidates the effect of sonication time in synthesizing NCs on its characteristics and plant use efficiency. For this purpose, a hard/soft nanocomposite (NC) (CoFe2O4/Ni0.8Cu0.1Zn0.1Fe2O4) was sonochemically synthesized at different sonication times (20 and 60 minutes) and comprehensively characterized. They were hydroponically applied to wheat seedlings (50, 100, 200, 400, and 800 mg/L). The physiological, morphological, and nutritional status of the seedlings were determined. The results showed that an increase in sonication time decreased the mean NC size: 26.7 nm (20 minutes) and 17.4 nm (60 minutes). Photosynthetic parameters, growth, and biomass were gradually reduced with the increasing NC concentrations, revealing their toxic effect. However, treating NCs at 60 min significantly improved the average root length, suggesting its beneficial role for plant growth at the germination stage. The content of elements in the composition of the NCs (Fe, Zn, Co, Ni, and Cu) was remarkably higher in the NC-treated roots compared to the untreated controls. In addition, 60 minutes of preparation showed better plant uptake than 20 minutes. This is the first study to evaluate the effect of sonication time in the preparation of NC on plant nutrition and their fate in plants