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Ab initio within the full potential linearized augmented plane wave (FP-LAPW) method with the GGA+U approach is applied to study the electronic structures of two compounds NaK3(NpO2)4(SO4)4(H2O)2 and NaNpO2SO4H2O. The present calculations show that the major part of the spin magnetic moment in these two compounds is from Np(V) ions, and the origin of the cation-cation interactions between Np comes from the spin polarization effect within Np-ONp-Np bonds.

Ti substituted BiFe 1− x Ti x O 3+ δ films have been prepared on indium–tin oxide (ITO)/glass substrates by the sol–gel process. The films with x =0.00–0.20 were prepared at an annealing temperature of 600 °C. X-ray diffraction patterns indicate that all films adopt R3m structure and the films with x =0 and 0.10 show pure perovskite phase. Cross-section scanning shows the thickness of the films is about 300 nm. Through 0.05 Ti substitution, the 2 P r increases to 8.30 μC/cm 2 from 2.12 μC/cm 2 of the un-substituted BiFeO 3 film and show enhanced ferroelectricity at room temperature. The 2 P r values are 2.63 and 0.44 μC/cm 2 for the films with x =0.01 and 0.2, respectively. Moreover, the films with x =0.05 and 0.10 show enhanced dielectric property since the permittivity increases near 150 at the same measuring frequency. Through the substitution of Ti, the leakage conduction is reduced for the films with x =0.05–0.20.

A kinetic Monte Carlo (kMC) simulation is conducted to study the growth of ultrathin film of Co on Cu(001) surface. The many-body, tight-binding potential model is used in the simulation to represent the interatomic potential. The film morphology of heteroepitaxial Co film on a Cu(001) substrate at the transient and final state conditions with various incident energies is simulated. The Co covered area and the thickness of the film growth of the first two layers are investigated. The simulation results show that the incident energy influences the film growth and structure. There exists a transition energy where the interfacial roughness is minimum. There are some void regions in the film in the final state, because of the influence of the island growth in the first few layers. In addition, there are deviations from ideal layer-by-layer growth at a coverage from 0 similar to 2 monolayers (ML).

Cu3N and Al x Cu3N films were prepared with reactive magnetron sputtering method. The two films were deposited on glass substrates at 0.8 Pa N2 partial pressure and 100 °C substrate temperature by using a pure Cu and Al target, respectively. X-ray diffraction (XRD) measurements show that the un-doped film was composed of Cu3N crystallites with anti-ReO3 structure and adopted [111] preferred orientation. XRD shows that the growth of Al-doped copper nitride films (Al x Cu3N) was affected strongly by doping Al, the intensity of [111] peak decreases with increasing the concentration of Al and the high concentration of Al could prevent the Cu3N from crystallization. AFM shows that the surface of Al x Cu3N film is smoother than that of Cu3N film. Compared with the Cu3N films, the resistivities of the Al-doped copper nitride films (Al x Cu3N) have been reduced, and the microhardness has been enhanced.

In this paper, the characterization of thin films, deposited with the precursor ferrocene (FcH) by the plasma enhanced chemical vapour deposition (PECVD) technique, was investigated. The films were measured by Scanning Electronic Microscopy (SEM), Atomic Force Microscopy (AFM), Electron Spectroscopy for Chemical Analysis (ESCA), and Superconducting Quantum Interference Device (SQUID). It was observed that the film's layer is homogeneous in thickness and has a dense morphology without cracks. The surface roughness is about 36 nm. From the results of ESCA, it can be inferred that the film mainly contains the compound FeOOH, and carbon is combined with oxygen in different forms under different supply-powers. The hysteresis loops indicate that the film is of soft magnetism.

Copper nitride thin films were deposited on glass substrates by reactive direct current (DC) magnetron sputtering at various N2-gas partial pressures and room temperature. X-ray diffraction measurements showed that the films were composed of Cu3N crystallites and exhibited a preferential orientation of the [111] direction at a low nitrogen gas (N2) partial pressure. The film growth preferred the [111] and the [100] direction at a high N2 partial pressure. Such preferential film growth is interpreted as being due to the variation in the Copper (Cu) nitrification rate with the N2 pressure. The N2 partial pressure affects not only the crystal structure of the film but also the deposition rate and the resistivity of the Cu3N film. In our experiment, the deposition rate of Cu3N films was 18 nm/min to 30 nm/min and increased with the N2 partial pressure. The resistivity of the Cu3N films increased sharply with the increasing N2 partial pressure. At a low N2 partial pressure, the Cu3N films showed a metallic conduction mechanism through the Cu path, and at a high N2 partial pressure, the conductivity of the Cu3N films showed a semiconductor conduction mechanism.

(BiFeO3)1−x–(PbTiO3)x solution films have been prepared on LaNiO3/SiO2/Si substrates by the sol–gel process at an annealing temperature of 500 °C. X-ray diffraction patterns indicate that a cubic phase transition occurs in the film with x = 0.1. Cross section scanning shows the thickness of the films is about 470 nm. Coexistent ferroelectricity and magnetism at room temperature are observed by measuring ferroelectricity and magnetism. The study of ferroelectricity indicates that the remnant polarization and applicable drive field are increased by the ratio x of PbTiO3. The film with x = 0.05 has the maximum saturation magnetization. In addition, dielectric property as a function of frequency is studied.

We investigate the magnetic transitions in a (La1-xBx)(2/3)Ca1/3MnO3 system, which consists of paramagnetic and ferromagnetic domains, based on a magnetic theoretical percolation model. In the mean-field approximation, the resistance as a, function of temperature and magnetic field has been derived analytically and simulated numerically. It is found that the dependence of the critical temperature on magnetic field is linear when applied magnetic field is not too strong. Our theoretical predications are in good agreement with recent experimental observations.

Using an accurate density-function method, we explore the coexistence of the magnetism and conductivity in bis(ethylenediselena)-tetrathiafulvalene (BEST) with the paramagnetic hexacyanoferrate(III) [Fe(CN)6]3−or the photochromic nitroprusside anion [Fe(CN)5NO]2−. The total and partial densities of states, and the atomic spin magnetic moments are calculated and discussed. It is found that the up- and down-spin total densities of states (DOS) are continuous in the vicinity of the Fermi level, there is overlap between the HOMO and LUMO in the up-spin subbands and the down-spin subbands, which reveals that these types of compounds have conductive properties. From the total and partial densities of states and atomic spin magnetic moments, it is shown that the spin magnetic moments of (BEST)4[Fe(CN)6] is mainly assembled at the iron atom and the cyanogen radical, and the spontaneous magnetic moments for (BEST)2[Fe(CN)5NO] come from iron atom, cyanogen and nitric oxide radical. To our best knowledge, it is the first theoretical study on the coexistence of the magnetism and conductivity of these compounds.

With the help of the replica method and imaginary-time functional-integrate technique, the spin glass model with the vibrations of crystal lattices is investigated. In the limit of the replica symmetry and the imaginary-time static approximation, the magnetic and thermodynamic quantities have been obtained. By the numerical calculations, we found that the magnetization of the system has the typical spin-glass behaviour. A peak is found in the susceptibility–temperature curve and is shifted to lower temperature with increasing applied field. Due to the lattice contribution, the specific heat increases strongly at high temperature. Due to the magnetic contribution, the anomaly in the specific heat–temperature curve forms a λ-type peak, which agrees with the observation of Rojo et al. [Phys. Rev. B 66 (2002) 094406].

We investigate the electrical properties of Sm-doped Bi4−xSmxTi3O12 (BST) ceramics prepared by a conventional electroceramic technique. The x-ray diffraction analysis reveals the Bi-layered perovskite structure in all samples. The SEM micrographs show randomly oriented and plate-like morphology. For the samples with x = 0.4 and 1.0, the current–voltage characteristics exhibit negative differential resistance behaviour and the P–V hysteresis loops are characterized by large leakage current, whereas for the samples with x = 0.6 and 0.8, the current–voltage characteristics show simple ohmic behaviour and the P–V hysteresis loops are of the saturated and undistorted hysteresis. The remanent polarization and coercive field of the BST ceramic with x = 0.8 are above 32 μC/cm2 and 70 kV/cm, respectively.

We have studied the densification behaviour, microstructure and electrical properties of WO3 ceramics with V2O5 as the additive ranging from 0.5 to 15mol%. Scanning electron microscopic photos indicated that the grain size of WO3-V2O5 specimens is smaller than that of pure WO3. The addition of V2O5 to WO3 showed a tendency to enhance the densification rate and to restrict the grain growth. Electrical properties of all specimens were measured for different electrodes at different temperatures. The formation of the grain boundary barrier layer was confirmed by the non-ohmic I-V behaviour. The nonlinear coefficient was obtained at the current density J=0.01, 0.1 and 1mA/cm(2) for a series of WO3-V2O5 samples. The V0.5mol% specimen showed an abnormal phenomenon that the nonlinear characteristics appeared at 350degreesC and disappeared at lower and higher temperatures. This implies that it could be applied as a high-temperature varistor. The double Schottky barrier model was adopted to explain the phenomena for the WO3-V(2)o(5) varistors.

The full-potential linearized augmented plane wave (FPLAPW) method with the generalized gradient approximations (GGA) is applied to study the compound [Cu(NTTmPy)(2)(N-3)(2)](n) (NITmPy = 2 - (3' - Pyridyl) - 4,4,5,5 - tetramethylimidazolin - 1 - oxyl - 3 - oxide). The total density of states (DOS) and the partial density of states (pDOS) are calculated to explain the electronic and the magnetic properties of [Cu(NTTmPy)(2)(N-3)(2)](n). It is found that [Cu(NTTmPy)(2)(N-3)(2)](n) is stable in the ferromagnetic state and the magnetic moment of the molecule mainly comes from the Cu atoms (0.518 mu(B)) with partial contribution from N, O atoms of nitronyl nitroxide radicals. There exist orbital hybridization between 3d orbital of Cu and p orbitals of N(1) (from pyridyl rings of the NITmPy ligands) and N(4) (from azido group) and the weak direct exchange interactions between Cu and 0 atoms of nitronyl nitroxides. In addition, the bridging carbon atom (C(6)) carries a significant negative spin density (-0.019mu(B)). The sign alternation of the magnetic moment along the pyridyl ring is obtained, which agrees with experiments.

The full-potential linearized augmented plane wave method was applied to study the electronic and the magnetic properties of the compound pipz-H-2[MnF4(HF2)](pipz=piperazine). The band structure, the total density of states, the partial density of states and the electron density were calculated to explain the electronic and the magnetic properties of pipz-H-2[MnF4(HF2)] in the ferromagnetic state. It is found that the magnetic moment of the molecule mainly comes from the Mn atoms with partial contribution from the F atoms. The symmetrical sigma/sigma, bonds via H atoms along Mn-F-H-F-Mn chains and the weak direct-exchange interaction between F(2), F(3) and Mn atoms have effect on the electronic structure and the magnetism of pipz-H-2[MnF4(HF2)].

A new model — model of random porous media degradation via several fluid displacing, freezing, and thawing cycles is introduced and investigated in this paper. The fluid transport is based on the deterministic method with dispersion effect. The result shows that the topology and the geometry of the porous media have a strong effect on displacement processes. The cluster size of viscous fingering (VF) pattern in percolation cluster increases with the increase of iteration parameter n. When iteration parameter , VF pattern does not change with n. We find that the displacement fluid forms trapping regions in random porous media with dispersion effect. And the trapping regions will expand with the increasing of the iteration parameter n. When r (throat size) and , the peak value of the distribution increases as n increases, where is the normalized distribution of throat sizes after different displacement-damages but before freezing. The peak value of the distribution reaches a maximum when and , where is the normalized distribution of the size of invaded throat. This result is different from invasion percolation. It is found that the sweep efficiency E increases along with the increasing of iteration parameter n and decreases with the network size L, and E has a minimum as L increases to the maximum size of lattice. The VF pattern in percolation cluster has one frozen zone and one active zone.

The effects of polarons along main chain and spin-soliton-like along side-radical lattice in doped quasi-one-dimensional π-conjugated organic ferromagnets are studied by selfconsistent method. It is shown that the gap of spin-down and spin-up mid energy bands of the system decreases because new energy levels of localization states appear. The stability of organic ferromagnetic system is weakened with decreasing of the gap. In addition, it is also shown that there is charge transfer between main chain and side-radical lattice of the doped system.

The percolation clusters with varying occupy probability were constructed in this paper. Viscous fingering (VF) in percolation cluster, based on the assumption that bond radii are Rayleigh distribution, is investigated by means of successive over-relaxation technique. The fractal dimension for VF in percolation cluster is calculated. The result shows that it can increase fractal dimension of VF as increase of percolation probability of reduce of viscous ratio. VF's fractal dimension of porous media in the limit viscous ratio → ∞ is found to be identical with that in diffusion limited-aggregation. We have found that the topology and the geometry of the porous medium have strong effects on the displacement processes and the structure of the VF. We find that the sweep efficiency of the displacement processes mainly depends upon the length of the network system and also on the viscosity ratio. Moreover, the fractional flow of injected fluid as a function of mean saturation is obtained.

We report a comparative study between two kinds of polyaniline, PANI-H3PO4 and PANI-C4H6O6. We have measured the temperature dependence of the dc-conductivity σdc(T) and magnetic susceptibility χT(T). The structure of polyaniline was characterized by Fourier transform infrared technique, electron-spin-resonance and x-ray diffraction. Polyaniline synthesized with phosphoric and tartaric acids leads to high magnetic susceptibility χT (at T = 295 K) ≈ 10-4 emu/mol.2rings. The dc-conductivity of both kinds of PANI shows a semiconductor behavior and follows the quasi-one-dimensional variable-range-hopping model. A comparison of the magnetic susceptibility shows greater electron localization in PANI-C4H6O6, which is in agreement with the lower conductivity at room temperature for PANI-C4H6O6.

A computer model of capillary and viscous fingering in a porous media is presented, which treats the media as a square lattice connected with randomly chosen radius. The fractal properties of the model are studied for shell-shell aggregation method by Monte Carlo simulation. The simulation results show that the dimension D increases along with increasing of M and decreasing of mu, where M and mu are the ratios of the viscosity of the two fluids and the most probable radius of the throat in porous media respectively. It is found that there exist foul regions for fluid.

A new kind of organic polymer ferromagnet based on polaron is proposed. In this kind of polymer, there are no organic free-radicals, which are rather reactive and unstable, instead spins are provided by polarons. Allowing for full lattice relaxation, the system is studied self-consistently by Peierls-Hubbard model. The formation energies of polarons are calculated. The possible ferromagnetism in polymers of this type is demonstrated.

Based on a theoretical model proposed for quasi-one-dimensional organic polymer ferromagnet poly-BIPO, the effects of electron-electron interaction and electron-phonon coupling on the spin-density-wave (SDW) state of poly-BIPO system are studied. It is found that the SDW state is the stable ground state of the system, in which the system shows ferromagnetic order. And the larger electron-electron interaction and the smaller electron-phonon coupling will make the SDW state more stable than the nonmagnetic state.

A modified method of calculating the end-to-end distance of segments with a given number of units in a single polymer chain is presented and numerical studies of some fractals by using Havlin and Ben-Avraham's and our methods are given. The results show that our method can remove the fluctuations in the end-to-end distances of the segments arising in Havlin and Ben-Avraham's method.

A new computer model of viscous fingering (VF) in a porous medium is presented. The simulation results show that the VF pattern is in agreement with the experimental results. The simulation on the sweep efficiency also agrees with experiment results. The surface fractal dimension as a function of viscous ratio is found.

A new porous media model with correlated sites-bonds has been constructed. Taking into account both the pore and throat geometries, the viscous fingering (VF) in porous media has been investigated by using the standard over-relaxed Gauss-Seidel scheme. The simulation results show that the VF's structure varies with the correlation parameter epsilon and the viscous ratio M. The sweep efficiency epsilon decreases along with the increase of the correlation parameter E and the lattice size R-1s. The surface fractal D-s gradually increases as the correlation parameter epsilon increases, whatever the viscous ratio M is. Also, D-s gradually increases as M increases whatever epsilon is. This means that not only the viscosity ratio but also the topology and the geometry of the porous media have a strong effect on the displacement process, the VF's structure, the sweep efficiency and the surface pattern.

A model of random porous media degradation is investigated via several fluid displacing, freezing and thawing cycles. The fluid transport is based on the deterministic method with dispersion effect. Research shows that the topology and the geometry of the porous media have a strong effect on displacement processes. The distribution of throat size N(r) after displacement but before freezing damage shows that the major change, after successive cycles, happens at the throat radius r > 0.9. The distribution of velocities normal to the interface of viscous fingering in percolation cluster is also studied. When iterations n greater than or equal to 10, the scaling function distribution is very sharp.

Quantum transport quantities, based on the fracton-electron interaction, are calculated by using the Ha¨nsch-Mahan quantum transport equation. Compared with those given by the first order and second order interaction of the fracton-electron, a Hall conductivity expression at all temperatures is presented for any fractal structure.

The effect of low-energy deposition particles on the initial stage of thin film growth is studied by Monte Carlo simulation in this paper. The energy range of deposition particles is from 0 to 0.7eV. Three processes are considered: atom deposition, adatom diffusion and re evaporation. The effect of nearest adatoms and next near adatoms is also considered. The results show that the low-energy ion irradiation strongly affects the island film growth process at low temperature. Morphologies and size distributions of islands have significantly changed with the increase of incident ion energy.

In this paper, a method of calculating low-temperature Hall conductivity in a weak magnetic field by means of Mahan-Hansch transport equation including the external magnetic field is presented. Hall conductivity and Hall coefficient based on the s-d exchange interaction model are obtained. Compared with other calculations, our method overcomes the defect of the divergence of Hall conductivity at T = ok and kondo temperature T k isobtained. Our result is in good agreement with experiments.

The ferromagnetic state in quasi-one-dimensional organic ferromagnet poly-SIPO has been studied. We consider the electron hoping, electron-electron correlation and Pierls instability in one-dimensional system. And self-consistent calculations are performed to investigate the structure of energy band and the distribution of spin density. The effects of the above aspects on the ferromagnetic state are studied. The results show that the ground state is a stable ferromagnetic state in this system.

利用稳态量子ｒｅｐｌｉｃａ对称自旋玻璃理论，研究了具有Ｄｚｙａｌｏｓｈｉｎｓｋｉｉ－Ｍｏｒｉｙａ（缩写为ＤＭ）各向异性相互作用的Ｓｈｅｒｒｉｎｇｔｏｎ－Ｋｉｒｋｐａｔｒｉｃｋ自旋玻璃在外场中的热力学性质。数值计算了不同外场和各向异性作用的自旋为１／２和１的熵、比热、局域磁化率和相应的序参数随温度的变化。发现局域磁化率与热场动力学的结果相符合。特别地，本文的比热－温度曲线能满意地解释Ｂｒｏｄａｌｅ等实验观察到的不同磁场下的交叉特征。

The overlap of magnetization of the ground state in a RKKY spin glass system with the Dzyaloshinsky-Moriya interaction is studied based on the theory of infinite number of order parameter. It is shown that the nonmagnetic impurities are coupled with the host lattice. The results are in good agreement with experiments.

In this paper we calculated the phonon density of states and the neutron scattering factor in a model of a random polymer chain embedded as a self-avoiding walk on a diamond lattice by using the equation of motion method of Green's function. The Hamiltonian of the model includes stretching force, bending force and dihedral force. The result showed that the gap near disappeared, which is in good agreement with experiment. It is also found that peaks of the spectrunr at low frequencies are sensitive to the degree of crystallization. This indicates that they are related only to the vibration of the crystalline region.

The numerical simulation of the irreversiblity of magnetization and the anisotropy field is studied in a spin glass with RKKY and DM interactions. It is found that the anisotropy field increases linearly with the concentration of nonmagnetic impurities, but the remanent magnetization and the saturation remain unchanged with different concentrations. A comparison is made with experiment.

Simultaneous studies of the conductivity and the clasticity exponents on Sierpinski carpet made of metal and voids are reported. The elasticity exponent is β=0.29±0.01, the conductivity exponent α=0.22±0.01. It is obvious that they belong to different universality classes.