A Volt-Second Source for Calibration of Integrator in a Pulsed Field Magnetometer

A volt--second (Vs) source intended for absolutely calibrating the integrator in a pulsed field magnetometer (PFM) is designed and proven to be with accurate rising and falling edges and reasonable lower uncertainty. A comparison experiment shows that the difference between the magnetic fluxes generated respectively by the Vs source and the mutual inductor is within ±0.04%. The PFM is then calibrated in an absolute way of the Vs source. The calibrated PFM gives the measured results in good agreement with a static BH tracer supplied by National Institute of Metrology of China and provides a convenient way of studying the effect of mathematic process on the dynamic measuring curve of PFMs.     

A new generation of CMOS-compatible high frequency micro-inductors with ferromagnetic cores: Theory,fabrication and characterisation

A new generation of CMOS-compatible micro-inductor prototypes with magnetic cores were realized, characterised as well as theoretically modelled in a frequency range up to 4 GHz, a frequency range where, e.g., mobile communication and global positioning systems (GPS) are operated. The micro-inductor's electrical magnitudes like inductance (L) and quality factor (Q) were theoretically described by means of an equivalent circuit model taking the frequency behaviour of the magnetic film core, expressed by the Landau-Lifschitz and Maxwell equations, into account. Six inch targets were used to deposit metallic layers (Al₉₉Si_0.5Cu_0.5), diffusion barriers (Si₃N₄), insulating layers (SiO₂) and magnetic films (Fe₃₉Co₃₀Ta₈N₂₃) by DC or reactive r.-f.-magnetron sputtering. All film materials were patterned by NUV-lithography (Near Ultra Violet), plasma beam milling and reactive ion etching to form the micro-inductors on 4-inch silicon wafers. The inductor windings are arranged in a way that they possess a low resistance and generate a quasi closed flux at the end of the cores to minimise eddy current losses in the silicon substrate. In order to diminish demagnetising effects in an efficient working core the magnetic films were patterned into micro squares with lateral dimensions of 20 and 100 μm with 100 nm in thickness. More magnetic volume and a higher micro-inductor cross-section was achieved by producing 100 nm magnetic double layers separated by a 800 nm thick Si₃N₄ inter-layer. To guarantee a sufficiently high cut-off frequency of the magnetic films, they were annealed in a static magnetic field at a temperature of 400 °C for uniaxial anisotropy induction. This represents a temperature treatment where aluminium CMOS processes take place. As a result of patterning, the magnetic film material exhibited a remarkable increase of the cut-off frequency from 2 GHz in laterally extended films up to 3.2 GHz which could be also observed in the measured frequency dependent inductance and quality factor. This was accompanied by an acceptable decrease of the initial permeability that still enabled initial inductances between 1 and 2 nH to be attained.     

Non-Smooth Bifurcation and Chaos in a DC-DC Buck Converter

A direct-current-direct-current （DC-DC） buck converter with integrated load current feedback is studied with three kinds of Poincaré maps. The external corner-collision bifurcation occurs when the crossing number per period varies, and the internal corner-collision bifurcations occur along with period-doubling and period-tripling bifurcations in this model. The multi-band chaos roots in external corner-collision bifurcation and often grows into 1-band chaos. A new kind of chaotic sliding orbits, which is more complex for non-smooth systems, is also found in this model.     

Mobility of interstitial oxygen in scandium by anelastic spectroscopy

The high-temperature anelastic spectrum of the solid solution Sc-O has been investigated on a polycrystalline sample at oxygen concentrations between 0.024 and ∼0.9 at.% O, as estimated by residual resistivity and intentional O doping. Two thermally activated relaxation processes appear near 430 and 520 K for a vibration frequency of 3.5 kHz; both peaks are stable with thermal cycling and their intensities increase with the oxygen content, indicating that they are due to O jumps. The process at lower temperature has an intensity that strongly increases with increasing temperature, when measured at higher frequency (42 kHz), indicating that the relaxation occurs between states differing in energy by ∼0.3 eV. The peak is describable by a single relaxation time, and is interpreted as due to the stress-induced hopping of single oxygen atoms between the non-equivalent tetrahedral and octahedral interstitial sites. The process at high temperature is tentatively attributed to O pairs. An estimate of the specific resistivity of O atoms has been provided.     

Development and Characterization of Metal-Insulator-Metal Capacitors with SiNx Thin Films by Plasma-Enhanced Chemical Vapor Deposition

We report the fabrication of high breakdown voltage metal-insulator-metal （MIM） capacitors with 200-nm silicon nitride deposited by plasma-enhanced chemical vapor deposition with 0.957 SiH4/NH3 gas mixing rate, 0.9 Torr working pressure, and 60 W rf power at 250℃ chamber temperature. Some optimized mechanisms such as metal source wiping, pre-melting and evaporation rate adjustment are used for increasing the yield of the MIM capacitors. N2 annealing and O2/H2 plasma pre-deposition treatment is proposed to increase the reliability of the MIM capacitors in high-temperature, high-pressure, and high-humidity environments. A 97% yield and up to 148 V breakdown voltage of a 13.06pF MIM capacitor with 0.04 mm^2 die area can be fabricated.     

Resistive hysteresis and capacitance effect in NiFe2O4/SrTiO3: Nb(1 wt%) junctions

Epitaxial ultrathin NiFe₂O₄ films were deposited on 1 wt% Nb-doped SrTiO₃ (0 0 1) substrates by reactive cosputtering to form junctions with an area of ∼2 mm², and current-voltage curves show rectifying and asymmetrical hysteresis characteristics. The resistance calculated from the current-voltage curves is strongly voltage dependent, and the hysteretic loops with high and low resistive states were observed. The hysteretic loops are considered to stem from the capacitance effect of the highly resistive NiFe₂O₄ layer, which leads to charge accumulation at the interfaces. The results show that the interfaces of the junctions have a large areal capacitance of ∼100 nF/mm² from 300 to 120 K.     

Magnetic permeability and microstructure of the Bi,Si oxides-doped NiZnCu ferrite composite material

Bi,Si oxides-doped NiZnCu ferrite composite material has been fabricated with different sintering times. The microstructure of the samples was investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The complex permeability has been measured up to 1 GHz by the impedance analyzers. The complex permeability has been simulated based on the magnetic circuit model, and the result was compared with the experimental results. In the low-frequency region, the real part of the permeability of the composite material is lower than the one of non-doped NiZnCu ferrite, on the other hand it is higher than non-doped sample in the high-field region. The peak position of the imaginary part is shifted to higher frequency in the composite material.     

Phase Diagram and Phase Separation of a Trapped Interacting Bose-Fermi Gas Mixture

In six different regimes for a spatial phase diagram of a trapped interacting Bose-Fermi gas mixture at low temperatures, we present the conditions for the spatial demixing and separation of bosons and fermions. Starting from a semiclassically thermodynamic model for the local density functional of thermal bosons and fermions,the explicit analytical expressions for the fugacities of bosons and fermions are derived in different regimes by means of a first-order perturbation method in a local-density approximation. The critical values of the fermionboson interaction strength as a function of the fractional composition of fermions have a general feature: increase,extreme and decrease with increasing the fermionic composition slightly above Bose-Einstein critical temperature.     

High-momentum tail in the Tonks-Girardeau gas under general confining potentials

We prove that the ground state momentum distribution of a one-dimensional system of impenetrable bosons exhibits a k⁻⁴ tail for any confining potential. We also derive an expression for easily computing the asymptotic occupation numbers and verify our results with an exact numerical approach.     

The evolution of magnetic,electrical and structural properties of nanogranular [FeCoBN/SiN]×n thin films

Some results concerning the magnetic, electrical and microstructural properties of multilayer [FeCoBN/Si₃N₄]×n films in view of their utilization for manufacturing thin film magnetic inductors are presented. A comparison between the magnetic, electrical and structural properties of FeCoBN and [FeCoBN/Si₃N₄]×n thin films is also reported. The [FeCoBN/Si₃N₄]×n thin films with the thickness of the FeCoBN layers varied from 10 to 30 nm, exhibit good soft magnetic characteristics and high values for electrical resistivity such as Ms of 172–185 A m²/kg, Hc of 318–1433 A/m and ρ of 82–48×10⁻⁷ Ω m, respectively. These physical properties of the samples are discussed in relation with the microstructure of the multilayer system.     

Anomalous magnetic antiresonance and resonance in ferrite nanoparticles embedded in opal matrix

Observation of magnetic antiresonance phenomenon is reported in 3D opal nanocomposite with embedded ferrite particles. Antiresonance at microwave frequencies of millimeter waveband was observed. It results in a sharp maximum of the reflection coefficient of an electromagnetic wave. Measurements were carried out in the frequency range from 26 to 38 GHz for two compositions of embedded ferrite particles, namely, the Co_0.5Zn_0.5Fe₂O₄ and Ni_0.5Zn_0.5Fe₂O₄. The physical nature of antiresonance is discussed.     

Frequency characterization of thin soft magnetic material layers used in spiral inductors

The paper details the characterization of thin magnetic materials layers, particularly soft materials, with respect to their behaviour in frequency (from 10 MHz to 1 GHz). The proposed method is suitable for any soft but insulating magnetic material; Yttrium Iron Garnet (YIG) is used as an example. The principle is based on a comparison between simulations for different values of the permeability and measurement values versus frequency of planar inductor structures; an experimental validation is proposed as well. Thin magnetic material is first deposited on an alumina substrate using RF sputtering technique; a planar spiral winding of copper is then deposited on the magnetic material by the same technique. The effective permeability versus frequency is obtained by comparing two samples of spiral windings with and without magnetic material. Network analyser measurements on samples of various geometrical dimensions and of different thicknesses are necessary to determine the effective magnetic permeability; we have obtained a relative effective permeability of about 30 for seven turns spiral inductor of a 17 μm YIG film.     

Information traffic in scale-free networks with fluctuations in packet generation rate

We study the information traffic in scale-free networks where the information generation rate varies with time as a periodic function. We observe that when the fluctuation in packet generation rate increases, the average transit time increases and network performance degrades. In order to improve the transportation efficiency in this situation, we propose a new routing method called mixed routing. It operates in two modes: (1) when the packet generation rate is small, the shortest paths are used to deliver the packets to the destination; (2) when the packet generation rate is large, the traffic loads in central nodes are redistributed to other non-central nodes, using the so-called efficient routing method. We find that the time shifting between the two modes is very critical for the routing performance. Consequently, we provide an efficient method to determine the critical times to shift the routing modes for achieving good network performance.     

Threshold electrical switching in As45Te55-xInx and As50Te50-xInx glasses

The electrical switching behaviour of As₄₅Te_55-xIn_x (5≤x≤15) and As₅₀Te_50-xIn_x (2.5≤x≤11.5) has been studied over a wide range of compositions. These glasses are found to exhibit threshold switching. The composition dependence of switching voltage (V_t) has been found to exhibit a change in slope and a local minimum at compositions x=10 and 12.5 for As₄₅Te_55-xIn_x and x=7.5 and 10.8 for As₅₀Te_50-xIn_x, respectively. The slope change in V_t verses x and the local minimum have been identified using two network topological effects, namely the rigidity percolation threshold and the chemical threshold. Received: 23 August 2001 / Accepted: 27 August 2001 / Published online: 11 February 2002     

Ground Band and Excited Band of Spin-1 BEC in Cigar Shaped Laser Trap

The wavefunctions that conserve the total spin are constructed for the fully condensed states and the states with one particle excited. A set of equations are deduced for the spatial longitudinal wavefunctions and the chemical potentials. These equations are solved numerically for ^23Na and ^87Rb condensates. The deformed trap shows significant effects on the spectrum. This implies that the spin effect of the spinor BEC are more easily detected in an optical trap of larger aspect ratio.     

Collapse of triaxial bright solitons in atomic Bose-Einstein condensates

We study triaxial bright solitons made of attractive Bose-condensed atoms characterized by the absence of confinement in the longitudinal axial direction but trapped by an anisotropic harmonic potential in the transverse plane. By numerically solving the three-dimensional Gross-Pitaevskii equation we investigate the effect of the transverse trap anisotropy on the critical interaction strength above which there is the collapse of the condensate. The comparison with previous predictions [A. Gammal, L. Tomio, T. Frederico, Phys. Rev. A 66 (2002) 043619] shows significant differences for large anisotropies.     

Dynamics of kicked matter-wave solitons in an optical lattice

We investigate effects of the application of a kick to one-dimensional matter-wave solitons in a self-attractive Bose-Einstein condensate trapped in an optical lattice. The resulting soliton’s dynamics is studied within the framework of the time-dependent nonpolynomial Schrödinger equation. The crossover from the pinning to quasi-free motion crucially depends on the size of the kick, strength of the self-attraction, and parameters of the optical lattice.     

Periodic spin domains of spinor Bose-Einstein condensates in an optical lattice

The periodic spin domains of spinor Bose-Einstein condensates confined in a one-dimensional optical lattice are studied in terms of the equation of motion of the spinor which is reduced to the nonlinear Schrödinger equation with the help of Holstein-Primakoff transformation. It is shown that the spin domains obtained analytically can be easily controlled by adjusting the light-induced dipole-dipole interaction, which is realizable in optical lattice created by red-detuned laser beams with modulating intensity. The dynamical stability of the spin domains is also demonstrated.