International Journal of Modern Physics B

Perovskite structured ferroelectric (Na_1/2 Bi_1/2)_0.945Ba_0.055TiO₃ (BNBT-5.5) material has been synthesized by the conventional sintering technique. X-ray analysis on the material showed a single phase compound with rhombohedral structure with lattice parameters a = 3.89 Åand α = 89.893 Å. Frequency and temperature dependence of dielectric permittivity, impedance, modulus and conductivity have been performed in the frequency and temperature range 45 Hz–5 MHz and 35–595^°C, respectively. The observed low frequency dielectric dispersion (LFDD) in the material could be explained by Jonschers power law and evaluated activation energies at different temperature regions. Impedance spectroscopy study showed the presence of both bulk and grain boundary effects in the materials. The ac conductivity spectrum obeyed the Jonscher's power law. Modulus analysis indicated the possibility of hopping mechanism for electrical process in the system.

In this work, various nano-sized samples of Y₂O₃, Y₂O₃:Eu and Y₂O₃:Eu, Sr were prepared by urea solution combustion method. Then the resultant nanopowders were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and photo-luminescence emission spectra. Furthermore, the CIE color coordinate of samples were calculated from photoluminescence emission spectra. Results showed that by doping of strontium, the photoluminescence intensity and chromaticity of Y₂ O₃:Eu phosphor was enhanced while crystallite size was decreased.

Bilayers of Sm–Co/Fe have been fabricated on 70 nm Cr buffered Si(100) substrate at an elevated temperature of 650^°C by the help of DC and RF magnetron sputtering. Very thin layers (0–0.7 nm) of Ti were introduced at the interface of the Sm–Co and Fe phases. The samples were analyzed by X-ray diffraction (XRD) and alternating gradient magnetometer (AGM). All the samples showed strong exchange coupling and single phase behavior. The rise and fall in magnetization and energy product were observed with increasing Ti interlayer thickness. Energy product (BH)_max value was found increased by 44% for 0.2 nm Ti interlayer as compared to the sample without Ti layer at interface.

The Exp-function method with the aid of symbolic computational system can be used to obtain the generalized solitary solutions and periodic solutions for nonlinear evolution equations arising in mathematical physics. In this paper, we study the analytic treatment of the Zakharov–Kuznetsov (ZK) equation, the modified ZK equation, and the generalized forms of these equations. Exact solutions with solitons and periodic structures are obtained.

Silicon oxycarbide (SiCO) thin films were prepared by the RF reactive sputtering technique on n-type silicon substrates with the target of sintered silicon carbide (SiC), and high purity oxygen was used as the reactant gas. The as-deposited films were annealed at temperatures of 600^°C, 800^°C, and 1000^°C under nitrogen ambient, respectively. The films were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and photoluminescence (PL) spectrophotometer. The results show that annealing temperature plays an important role in the structure and photoluminescence of the films. The temperature 600^°C is the most favorable annealing temperature for SiO₂ crystallization and the formation of 6H-SiC crystal phase in the SiCO films. The intense PL peaks located at 375 nm and 470 nm are observed at room temperature. The origin of the PL was discussed.

We propose and prove a theoretical scheme of realizing programmable and controlled remote quantum-state unambiguous discrimination (UD) based on nonlocal system–ancilla unitary evolution. By decomposing the evolution process from the initial state to the final state, we first construct the required nonlocal unitary evolution, which is a nonlocal conditional rotation. Utilizing the entanglement property of Greenberger–Horne–Zeilinger (GHZ) class state, we then design a quantum network for implementing the controlled nonlocal conditional rotation gate, and thus provide a feasible physical means to realize the remote UD. The features of the scheme is that the particular pair of states of system (data register) that can be remotely and unambiguously discriminated is specified by the state of the ancilla (program register). Furthermore, a third side is included, who may participate the process of quantum remote implementation as a supervisor. When the quantum channel is partially entangled, the third one can rectify the state distorted by the imperfect quantum channel. The success probability of implementing this remote UD is also investigated.

In this paper we consider a four-level W-type atom interacting with a single-mode quantized electromagnetic field in the presence of the Kerr medium. The atom and the field are initially prepared in the excited state and coherent state, respectively. The influence of the Kerr medium on the N-order squeezing and Poissonian statistics is investigated. We found that the maximum value of squeezing decreases by increasing the order N. Also, we noticed that the Kerr-like medium decreases the amount of squeezing and increases the sub-Poissonian statistics.

In this paper, periodic parametric perturbations are used to control chaos in Liu system. By changing the frequency of the perturbation signal, Liu system can be guided to not only periodic motion but also hyperchaos. Phase diagram, bifurcation diagram, Lyapunov exponents spectrum and Poincáre map are used to analyze the dynamic behavior of the controlled system in the numerical simulations, which show the effectiveness of our method.

We investigate the transport properties of an interacting ring threaded by a magnetic flux and with Rashba spin-orbit coupling, based on a recently developed functional renormalized group technique. In the calculations of the electronic transport processes, the Coloumb On-site interactions are taken into account. For an interacting ring connected to two leads, we find that (i) for Φ_AC = 0, the behavior of transmission zero at Φ_AB = π is generic for the universal regime; (ii) for certain Φ_AC and Φ_AB, one can use the mesoscopic ring as spin filter even in the presence of the local interaction in the ring.

We present a scheme to realize both the zero-n and the zero-ϕ_eff gap in a one-dimensional photonic band gap structure containing metamaterials. The frequency dispersion of the effective electric permittivity and magnetic permeability of the metamaterials in the adjacent layers in one period are represented by the Drude model and the resonant model. The chosen structure is composed of alternate double-negative and double-positive layers which exhibit a zero-n gap in a certain frequency range whereas in a higher frequency range it behaves as alternate permittivity negative and permeability negative layers to exhibit a zero-ϕ_eff gap. Some properties and benefits of having the zero-n and the zero-ϕ_eff gap in the same physical system are discussed.

We studied the temperature dependence of the upper critical field H_c2(T) of Mg_1-xAl_xB₂ single crystals (x=0.024 and 0.092) using the two-band Ginzburg–Landau theory. We found that this theory can describe H_c2(T) very well in the broad temperature range. The values of the parameters obtained by fitting experimental data to the theory indicated that the anisotropy of the σ bands decreased with the Al concentration. Accordingly, the temperature dependence of the anisotropy ratio of H_c2(γ_H) systematically decreased, and for x=0.092, γ_H was nearly independent of temperature.

The Lotka–Volterra model of cyclic competitions among three species with noise was investigated by numerical simulations. Our results indicate that the multiplicative noise is responsible for the alternately sinusoidal competitive oscillations of species, the optimizations of response of the system via stochastic resonance, the spatial patterns and the temporal oscillations of the spatial correlation coefficients.

In this paper, the growth of a gas bubble in a supersaturated liquid is discussed for a constant and variable cases of surface tension effect. The mathematical model is solved analytically by using the method of Plesset and Zwick¹⁸ after modified it. The growth process is affected by: diffusion coefficient D, Jacob number J_a, surface tension σ, adjustment factor b and void fraction ϕ₀. The famous formula of Plesset and Zwick is produced as a special case of the results at some values of the adjustment factors. Moreover, for some values of the adjustment factors, good approximation is obtained when a comparison between our results and the result that produced by Hashemi et al., ⁹ who solved the problem with the method of combining variables.