Search

A trinuclear Mn(II) coordination complex Mn3(HEDTA)2·10H2O (EDTA=ethylene diamine tetraacetic acid) 1 has been synthesized and characterized by X-ray crystal structure determination. In addition, IR spectrum, thermogravimetric analysis, electron paramagnetic resonance (EPR) spectra and magnetic susceptibility of this complex are discussed. X-ray determination indicates that six- and seven-coordinate modes between Mn(II) and H4EDTA exist alternately in 1. Furthermore, detailed discussion of magnetic ordering in the temperature range of 2∼300 K reveals the antiferromagnetic interactions in the complex.

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.

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.

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.

The thin-film growth process on a triangular lattice surface is studied by a Monte Carlo simulation (MCS). Four kinetic processes are considered: atom deposition, adatom diffusion, adatom nucleation and adatom reevaporation. We pay close attention to the substrate temperature and the interaction between the adatom and neighboring particles. The interaction energy between the adatom and the neighboring atoms around it is calculated by the Morse potential. The results show that the higher the temperature, the more compact the island. As the temperature is low, the film growth becomes fractal growth. At higher temperature, the island becomes more regular in shape that resembles the surface morphology.

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 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.

The localized vibrational modes around a bipolaron in cis-(CH)x are studied by using a two-dimensional extension of the SSH model that includes the bond-bending term. A number of additional modes have been found, compared with the results based on the standard SSH model. The amplitudes of the two directions (x and y direction) are comparable for most of the modes as in the trans-(CH)x case. The number of localized modes and their frequencies depend not only on the coupling constant, but also on the bond-bending term and the parameter t1 in removing the degeneracy of the ground 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.

Using the full-potential linearized augmented plane wave method based on the density functional theory, spin-polarized calculations of electronic structure for the zinc-blende CrS and CrSe are performed. Zinc-blende CrS and CrSe at their respective equilibrium lattice constants are half-metallic with the same total magnetic moment of 4.00B. The electronic structures of zinc-blende CrS and CrSe are calculated under uniform strains from -10% to +10% relative to the equilibrium lattice constant. The calculated results indicate that zinc-blende CrS and CrSe can maintain half-metallic ferromagnetism and keep the same total magnetic moment of 4.00B from -1% to 10% and from -4% to 10% uniform strain, respectively.

Based on our interchain coupled theoretical model for quasi-one-dimensional organic ferromagnet, we took into account the nearest and the next nearest hopping interactions between neighboring chains, to study the charge density wave and the spin density wave along the main chain. The calculated results showed that the interchain coupling results in the transfers of charge density and spin density between the main chain and the side radicals of the two coupled chains.

Starting from the extensional discrete model SSH Hamiltonian containing an external Coulomb potential arising from interchain charged solitons and the counterions, the intrachain electron-electron interaction, the energy spectra and electron states of soliton lattice have been studied in trans-polyacetylene. The results show that: two bound states have been found at the bottom of valence band and several other states at the top of conduction band. With the increasing of the dopant concentration, the localization of bound states are weakened and the discrete soliton energy levels in the forbidden band move into the soliton band. When the dopant concentration is up to 16.67%，all the discrete electron states of soliton lattice disappear and become extended ones. It is found that the forbidden band width increases and the gap (between the top of the soliton band and the bottom of conduction band) namows with the doping level increasing. Furthermore, the gap (from the bottom of the soliton band to the top of valence band) has a maximum at the critical doping level. Finally, the effect of e-e interaction on the energy spectra of soliton lattice is discussed.

On the basis of the diagnostics about the axial distribution of plasma electron temperature and electron density in an axial flow RF PCVD reactor by using electrical probe, a model for two-dimension fluid kinetics concerned with major PCVD parameters is proposed. A kinetic analysis about how deposition profiles are influenced by major PCVD parameters is presented by means of the analysis of plasma parameters. The model has been applied to study the deposition process of SnO2 films obtained from a gases mixture of SnCl4 and O2. The theoretical calculation are in good agreement with the experiments of deposition.

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.