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Physical properties of polycrystalline ferroelectrics including the contributions of the fixed dipolar defects and the average grain size in the Potts-Ising model are simulated by using the Monte Carlo method. Domain pattern, hysteresis loop and switching current of the polarization reversal process are obtained. Two processes are considered in our simulation. In the first one, the grain texture of ferroelectric ceramics are produced from the Potts model, and then the Ising model is implemented in the obtained polycrystalline texture to produce the domain pattern, hysteresis loop and switching current. It is concluded that the defect has the ability to decrease the remnant polarization Pr as well as the coercive field Ec. The back switching is obviously observed after the electric field is off, and it shows some variation after introducing the fixed dipolar defect. Meanwhile, the spike of the switching current is found to lower with the increasing defect concentration and the decreasing average grain size.

High quality Co-doped ZnO thin films are grown on single crystalline Al2O3(0001) and ZnO(0001) substrates by oxygen plasma assisted molecular beam epitaxy at a relatively lower substrate temperature of 450°C. The epitaxial conditions are examined with in-situ reflection high energy electron diffraction (RHEED) and ex-situ high resolution x-ray diffraction (HRXRD). The epitaxial thin films are single crystal at film thickness smaller than 500 nm and nominal concentration of Co dopant up to 20%. It is indicated that the Co cation is incorporated into the ZnO matrix as Co2+ substituting Zn2+ ions. Atomic force microscopy shows smooth surfaces with rms roughness of 1.9 nm. Room-temperature magnetization measurements reveal that the Co-doped ZnO thin films are ferromagnetic with Curie temperatures TC above room temperature.

We investigate the re-exciting process of a soliton, a polaron and a bipolaron in conjugated polymers. For a soliton case, the processes S0+h?S?+P and S?+h?S0+P? will take place, where S0, S? and P? express a neutral soliton, charged solitons and charged polarons, respectively. For a polaron case, the processes P?+h?P+BP?2 will occur, where BP?2 expresses a charged bipolaron with two electronic units. For a bipolaron case, the processes BP?2+h?P?+P? and BP?2+h?BP?2+E0 are obtained.

We investigate the variations from as-deposited Zn1−xCoxO magnetic semiconductors to the post-annealed Co–ZnCoO granular composite. The as-deposited Zn1−xCoxO magnetic semiconductor deposited under thermal non-equilibrium conditions is composed of Zn1−xCoxO nanograins of high Co concentration. The room-temperature ferromagnetism with high magnetization and large negative magnetoresistance are found in the as-deposited samples. By annealing, the samples become of granular composite consisting of the Co metal grains and the remanent Zn1−xCoxO matrix. Although the magnetization is enhanced after annealing, the spin-dependent negative magnetoresistance disappears at room temperature. The magnetoresistance observed in the annealed samples in the high field region has no relation with the ferromagnetism, which in turn indicates that the room-temperature ferromagnetism and large negative magnetoresistance observed in the as-deposited are the intrinsic properties of the Zn1−xCoxO magnetic semiconductor.

We prepare 2×(NiFe/CoZnO)/ZnO/(CoZnO/Co)×2 spin valve structures used for spin injection by sputtering and photolithography. In the junctions, the free magnetic layer 2×(NiFe/CoZnO) and the fixed magnetic layer (CoZnO/Co)×2 are used to realize the spin valve functions in the external switch magnetic field. Since the wide gap semiconductor ZnO layer is located between the two magnetic semiconductor layers CoZnO, the electrical spin injection from the magnetic semiconductor CoZnO into the non-magnetic semiconductor ZnO is realized. Based on the measured magnetoresistance and the Schmidt model, the spin polarization ratio in the ZnO semiconductor is deduced to be 11.7% at 90 K and 7.0% at room temperature, respectively.

Reverse polarization in polythiophene under an applied electric field has been studied in the framework of the tight-binding model. It is found that the applied electronic field has a great influence on the excited states of polythiophene. The effect of the heteroatoms on the polarization has been calculated and analysed carefully. It is indicated that a reverse polarization of biexcitons in polythiophene will be observed more easily. The heteroatoms increase this reversed polarization strength apparently.

Polaron tunnelling is studied in xPA/nPPP/xPA (PA for polyacetylene and PPP poly (p-phenylene)) triblock copolymer, which has a well–barrier–well structure. An extended tight-binding Hamiltonian including external electric field is adopted. Without electric field, the injected electrons would not extend over the whole copolymer chain but instead be confined in the segments of PA. This is different from the behaviour of the traditional semiconductors. It is found that the polaron can transfer to the potential barrier-PPP segment when the applied electric field reaches a certain value. The critical polaron tunnelling electric fields depend upon the lengths of PPP segments.

A tight-binding calculation to describe the triblock copolymer xPA(polyacetylene)/nPPP (poly(p-phenylene))/yPA or xPPP/nPA/yPPP is presented. The interfacial coupling between homopolymer segments is attributed to the hopping of π-electrons and the coupling of σ-bonds. The dependence of the band gap of triblock copolymers on the interfacial couplings or on the composite segment lengths is studied. The influence of composite segment lengths on the electron density is also studied. For nPPP/xPA/nPPP structures, the band gap varies with PA segment length over a wide range of 1.32-2.74eV. For nPA/xPPP/nPA structures, the band gap is invariant with PPP segment length. It is found that a spontaneous tunnelling phenomenon could take place in nPA/xPPP/nPA structures. Furthermore, the polaron caused by doping an electron into nPA/xPPP/nPA will tend to be confined in one of the well (PA) parts. This kind of confinement may increase the electron-hole recombination probability.

The persistent current and transmission of two connected Aharonov–Bohm rings coupled to external leads are solved analytically. The conditions on which we may observe persistent current, zero or perfect transmission as well as Fano resonance are studied.

The electronic properties of xPA/nPPP/yPA sandwiched copolymers with a well-barrier-well structure have been studied by using a tight-binding calculation. It was found that the electronic properties of the neutral states of these sandwiched copolymers are sensitive to the constitutions of PPP and PA monomers and the interface coupling between PA and PPP. It is verified that the quantum tunnelling effect will occur at the lowest conductive state of xPA/nPPP/xPA copolymers.

Magnetic multilayers [Co-Nb(1.5 or 3.6 nm)/Pd(x nm)]40 were fabricated by radio frequency sputtering synthesis. The structures and magnetic properties of the Co-Nb/Pd multilayers were studied by x-ray diffraction, vibrating sample magnetometer, torque magnetometer and ferromagnetic resonance measurements. The oscillatory dependence of the phase structure, the strain, the ferromagnetic interlayer coupling and the spacer polarization of multilayers on the increase of Pd spacer thickness was observed. The relationship among phase structure, strain, interlayer coupling and the polarization of Pd spacers was discussed. The magnetic polarization of Pd spacers will enhance the ferromagnetic coupling between magnetic layers and will restrain antiferromagnetic coupling to occur. The spin-dependent electron transport along the normal direction of multilayers and its exchange interaction play key roles in causing these oscillatory behaviors.

Magnetic multilayers [Co(1.5 nm)/Pd(x nm)]40 grown by rf sputtering were studied by x-ray diffraction, vibrating sample magnetometer, torque magnetometer and magnetoresistance measurements. The dependences of the interfacial roughness and the structure perfectness of Co/Pd multilayers on the spacer Pd layer thickness have been revealed from x-ray diffraction data. An oscillatory variation of saturation magnetization versus the thickness of the Pd spacer was observed. A similar oscillatory behavior in the dependence of its magnetic anisotropy on the thickness of the Pd spacer was observed. It is suggested from these two phenomena that the magnetic polarization of Pd spacers oscillates between ferromagnetic and antiferromagnetic polarization with the increase of Pd spacer thickness under a RKKY-like interaction. Evidence is found for the antiferromagnetic polarization of the inner-part of the Pd spacer. The antiferromagnetic coupling between two Co layers and giant magnetoresistance effect in Co/Pd multilayer system were not observed. The relationship among structure, interlayer coupling and magnetic polarization effect of the Pd spacer was discussed.

The stopping power of an electron gas for hydrogen ions is calculated based on the full self-consistent nonlinear density-functional frame. Three different configurations of hydrogen ions are considered and a criterion to test the validity of the self-consistent calculation is proposed. Comparison of calculation with available experimental data shows good agreement.

An oscillatory behavior in specific saturation magnetization of Fe/Pd multilayers is observed. The conversion electron Mossbauer spectroscopy and other experiments indicate that this behavior is caused by the magnetic polarization of Pd spacers, which alternates between positive and negative polarization with respect to the magnetic moments of Fe layers. The interlayer coupling between two Fe layers always keeps ferromagnetic. Then, the interlayer couplings in ferromagnetic metal/nearly ferromagnetic metal multilayers were calculated by using the model of Barnas. The results of calculation prove that the above phenomenon might appear under some condition. The influence of magnetic polarization potential of spacers and interface chemical potential on the interlayer couplings is also discussed.

[ZnO(0.5 nm)/Co(0.6 nm)]60 multilayers were fabricated by magnetron sputtering. The magnetic, transport and optical properties were studied. The ferromagnetic state at low temperature was demonstrated. Most of the grains in the samples will be unblocked when temperature is below 50 K. The measured magneto-resistance at 4.8 K is higher than 30%. This value is larger than any other reported data. The transport mechanism may come down to a combination of tunnelling conduction with the second-order hopping. Some small peaks on transmittance curves were found, the matter is still open.

Chemical adsorption and desorption of hydrogen atoms on single-walled carbon nanotubes (SWNTs) are investigated by using molecular dynamics simulations. It is found that the adsorption and desorption energy of hydrogen atoms depend on the hydrogen coverage and the diameter of the SWNTs. Hydrogen-adsorption geometry at the coverage of 1.0 is more energetically stable. The adsorption energy decreases with the increasing diameter of the armchair tubes. The adsorption and desorption energy of hydrogen atoms can be modified reversibly by externally radial deformation. The averaged C-H bond energy on the high curvature sites of the deformed tube increases with increasing radial deformation, while that on the low curvature sites decreases.

Nanogranular Fe0.35/(In2O3)0.65 films with complex magnetic structure were prepared by the rf sputtering method. An extra-large magnetoresistance up to 506% was obtained at 2.2 K, which is two orders of magnitude larger than that obtained at room temperature. This is related to the interaction with the impurities influencing the local magnetization, which is quite different from the spin-dependent tunnelling effect at room temperature. The interspacing Fe atoms dispersed in the In2O3 matrix play an important role in the transportation properties of carriers at low temperature.

The impact parameter dependence of electronic energy loss for heavy ions colliding at low velocity with atoms has been studied using the shell-wise local electron-density model. Roothaan-Hartree-Fock wave functions are used to calculate the local electron density of the atoms studied. The Brandt-Kitagawa effective stopping power charge theory is modified to incorporate the effective charge obtained using Fermi-level scattering phase shift calculations based on the density-functional formalism. The theoretical results are compared with available experimental measurements.

A molecular dynamics simulation method is used to study the growth of narrow single-wall carbon nanotubes. It is found that the growth temperature and the species of small carbon clusters in the feedstock are important for the quality of the nanotubes grown. There is a temperature range of 1000-1500 K in which the narrow armchair single-wall carbon nanotubes can grow rapidly via adduction of C2 dimers, even without the existence of catalysts. The narrow zigzag tubes cannot keep open-ended growth. If the feedstock consists of various species of carbon clusters, the tubes cannot keep open-ended growth. At higher temperatures, the narrow nanotubes close rapidly in the noncatalytic environment, and the products grown are fullerene-like capsules. PACS: 61. 46. +w, 36. 40. -c

A material asymmetry Co/Cu/Fe junction structure has been prepared for studying the spin-polarized electron injection at 77K. The sample performance was demonstrated to be analogous to that of a bipolar transistor. The maximal value of the output pulse voltage between Cu and Fe layers could reach the order of several μV when the bias current between Co and Cu layers was 10μA. The interface roughness, photograph of material, magnetic loop and injection characteristic curves have been measured. Some important points on this topic have been discussed.

This paper presents a new biometrics pattern, finger-articular back texture recognition using Log Gabor wavelet. Firstly, hand back image was captured by special imaging device. Then joint texture was segmented, and located by a sliding window. The texture features were extracted based on the Log Gabor wavelet transform and were classified by the corresponding feature encoding classifier. The experiment results shown that finger-articular back texture can be used for personal authentication, Log Gabor wavelet is better than Gabor wavelet for pattern extraction, and the equal right rate was 98.21% in Finger-articular back texture recognition.

Calculations of the magnetic domain structure (domain wall energy density, domain wall thickness, domain width and critical diameter of single domain particles) in Nd 2 Fe 14 B have been made by using its intrinsic parameters (lattice constants, magnetic moments of the atoms, Curie temperature, spontaneous magnetization and magneto-crystalline anisotropy constant). The four stages of magnetization reversal processes in oriented sintered Nd-Fe-B magnet after saturation magnetization along its easy direction are studied in detail in this paper. The results show that the nucleation of the reverse-magnetization nuclei in the surface layer of the grains of hard magnetic phase Nd 2 Fe 14 B, as well as the irreversible domain wall motion from the surface to the inside of the grains are dominant factors controlling the intrinsic coercivity of the Nd-Fe-B alloy.

A new approach is developed to calculate temperature dependent Seebeck coefficient of heavily doped systems by using Boltzmann transport theory and electron density of states (DOS) obtained from density functional calculations. This approach is applied to heavily doped La:STO with DOS from tetrahedral method and Fermi energy using Fermi integrals. The calculated Seebeck coefficient agrees with the experimental data nearly quantitatively, which proved the accuracy of this approach. The influence of the Fermi energy and asymmetry of DOS on the Seebeck coefficient is analyzed., Comment: 19 pages, 4 figures

The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAlO3/SrTiO3 (110). By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAlO3/SrTiO3 (110) heterostructure, the Ti—O octahedron distortions cause the Ti t2g orbitals to split into the two-fold degenerate dxz/dyz and nondegenerate dxy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t2g orbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaAlO3 and SrTiO3 leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAlO3/SrTiO3 (110).

The influence of surface polarity on the structural properties of BiFeO3 (BFO) thin films is investigated. BFO thin films are epitaxially grown on SrTiO3 (STO) (100) and polar (111) surfaces by oxygen plasma-assisted molecular beam epitaxy. It is shown that the crystal structure, surface morphology, and defect states of BFO films grown on STO substrates with nonpolar (001) or polar (111) surfaces perform very differently. BFO/STO (001) is a fully strained tetragonal phase with orientation relationship (001)[100]BFO||(001)[100]STO, while BFO/STO (111) is a rhombohedral phase. BFO/STO (111) has rougher surface morphology and less defect states, which results in reduced leakage current and lower dielectric loss. Moreover, BFO films on both STO (001) and STO (111) are direct band oxides with similar band gaps of 2.65 eV and 2.67 eV, respectively.

We give a brief introduction to the oxide (ZnO, TiO2, In2O3, SnO2, etc.)-based magnetic semiconductors from fundamental material aspects through fascinating magnetic, transport, and optical properties, particularly at room temperature, to promising device applications. The origin of the observed ferromagnetism is also discussed, with a special focus on first-principles investigations of the exchange interactions between transition metal dopants in oxide-based magnetic semiconductors.

ZnO thin film growth prefers different orientations on the etched and unetched SrTiO3(STO)(110) substrates. Inclined ZnO and cobalt-doped ZnO (ZnCoO) thin films are grown on unetched STO(110) substrates using oxygen plasma assisted molecular beam epitaxy, with the c-axis 42? inclined from the normal STO(110) surface. The growth geometries are ZnCoO[100]//STO[11?0] and ZnCoO[11?1]//STO[001]. The low temperature photoluminescence spectra of the inclined ZnO and ZnCoO films are dominated by D0X emissions associated with A0X emissions, and the characteristic emissions for the 2E(2G)?4A2(4F) transition of Co2+ dopants and the relevant phonon-participated emissions are observed in the ZnCoO film, indicating the incorporation of Co2+ ions at the lattice positions of the Zn2+ ions. The c-axis inclined ZnCoO film shows ferromagnetic properties at room temperature.

Titanium oxide ceramics doped with niobium is synthesized in reduced atmosphere at 1200 ℃ by conventional solid-state reaction technique. From their crystal structures determined by the powder X-ray diffraction(XRD), the samples have multiple-phase with low Nb concentration, but they have single tetragonal rutile phase when Nb content is larger than 0.02. The electrical conductivities, the Seebeck coefficients and the thermal conductivities of the samples with single phase are measured at a temperature range between room temperature and 900 K. The electrical conductivity and the Seebeck coefficient show non-metallic behaviors. According to the fitting, it is found that the samples show thermal-activation mechanism at low temperatures and small-polaron hopping conduction mechanism at high temperatures. Moreover, the analyses of XRD, electrical conductivity and Seebeck coefficient show that the concentration of oxygen vacancy decreases with Nb content increasing. Thermal conductivity decreases with temperature increasing, dominating by lattice thermal conductivity. In the measurement region, the figure of merit (ZT) reaches a highest value of 0.19 at 873 K in the Ti0.98Nb0.02O2- sample.

This paper proposes a universal spin-dependent variable range hopping theoretical model to describe various experimental transport phenomena observed in wide-band-gap oxide ferromagnetic semiconductors with high transition metal concentration. The contributions of the 'hard gap' energy, Coulomb interaction, correlation energy, and exchange interaction to the electrical transport are considered in the universal variable range hopping theoretical model. By fitting the temperature and magnetic field dependence of the experimental sheet resistance to the theoretical model, the spin polarization ratio of electrical carriers near the Fermi level and interactions between electrical carriers can be obtained.

Perovskite La0.9Sr0.1FeO3 ceramics have been synthesized at 1250℃，1300℃ and 1350℃ by the conventional solid-state reaction technique. From their crystal structures determined by powder X-ray diffraction，we found that the lattice volume decreases with increasing sintering temperature. The scanning electronic microscope (SEM) images of surface microstructures of the samples show that the average grain size increases with increasing sintering temperature. The electrical resistivity and Seebeck coefficient have been measured between room temperature and 800℃. At low temperatures，the electrical resistivity shows a semiconductivity-like behavior. With further increasing of temperature，the electrical resistivity slightly increases. An adiabatic hopping conduction mechanism of small-polarons is suggested from the temperature dependence of the electrical resistivity，which has different activation energies at low and high temperatures. The Seebeck coefficient rapidly decreases with increasing temperature，and reaches a saturation value about 600℃. With further increasing of temperature，the Seebeck coefficient slightly increases. With the increase of sintering temperature，the electrical resistivity decreases，while the Seebeck coefficient increases. Therefore，the power factor increases with increasing sintering temperature. The highest power factor of 90 μW/K2m was obtained at 727℃ for sample sintered at 1350℃.

Fe-doped In2O3 films are grown epitaxially on YSZ (100) substrates by pulsed laser deposition. The in-situ reflection high-energy electron diffraction, the atomic force microscopy, and the x-ray diffraction patterns show that the films have a well defined cubic structure epitaxially oriented in the (100) direction. Room temperature ferromagnetism is observed by an alternating gradient magnetometer. Strong perpendicular magnetic anisotropy with a remnant magnetization ratio of 0.83 and a coercivity of 2.5kOe is revealed. Both the structural and the magnetic measurements suggest that this ferromagnetism is an intrinsic property deriving from the spin-orbit coupling between the diluted Fe atoms.

Zn1−xFexO inhomogeneous oxide magnetic semiconductor films with high Fe concentration are prepared by sputtering, and fast annealing is carried out at different temperatures. It is found that magnetic properties are greatly modulated by controlling the composition inhomogeneity and subsequently fast annealing. Both ferromagnetic and paramagnetic components are found to coexist in the as-deposited Zn1−xFexO magnetic semiconductor. In particular, the antiferromagnetic coupling between the neighbouring local ferromagnetic regions is found in the as-deposited Zn0.23Fe0.77 O film, and the antiferromagnetic coupling strength increases with increasing temperature from 110 K to 300 K. We believe that this unusual antiferromagnetic coupling is mediated by thermally activated hopping carriers.

The possibility of forming cascading energy levels in SrTiO3 by doping Bi and Cu as an example is analyzed by using the density-functional-theory based first principles calculations of the electronic structure. The results show that both Bi doping and Cu doping can introduce a defect level in the forbidden band，and Co-doping of Bi and Cu can introduce two defect levels in the forbidden band. Electrons at the top of valence band can transit to the bottom of conduction band through a cascade transition process. Using the nonradiative transition model，we point out that the probability of electronic transition from the valence band to the conduction band through a cascade transition is much higher than that of direct transition from the valence band to the conduction band. The cascade transitions can effectively increase the carrier concentration in the conduction band.

There are important applications of metal in metamaterials. Three methods for dealing with metal in FDTD are analyzed and compared. ADE(auxiliary differential equation method) and PLRC(piecewise linear recursive convolution) have the same numerical result. However, there is a little difference between Sakoda's method and ADE. It is due to the error in calculation of convolution integral with Sakoda's method. Improving the convolution integral with the method used in PLRC, these three methods give the same results.

The Xα method is applied to study the spin-polarized electronic structures and atomic magnetic moments of clusters La8-xBaxCuO6 in the compound La2-yBayCuO4.This paper shows that Cu magnetic moment in La2CuO4 is 0.37μB, which is in better agreement with the experimental value(0.48±0.15μB). Ba substitution lowers the structure symmetry, removes molecular orbital degeneracy, and hence strengthens orbital hybridization and weakens quasi-two-dimensional feature, which enhance the coupling between Cu-O layer and the neighbormg layers and influence the charge transfer. These changes strongly affect the properties of carriers. Holes are introduced due to Ba substitution and they mainly enter into O sites, a few d-electronic holes enter into Cu sites, which causes important effects on the density of states, atomic magnetic moment and valence states of Cu and O in Cu-O layers. The results confirm that the holes are not always beneficial to the superconductivity. At the beginning the holes are beneficial to the superconductivity; they can decrease the superconductivity when more holes are introduced. This paper can explain that the transition temperature of high-temperature superconductive oxides changes with the variation of the doping level.

La0.67Ca0.33MnO3 films with thickness between 25 and 400nm were fabricated on (001) SrTiO3 and (001) LaAlO3 substrates, using pulsed laser deposition. The magnetization and resistivity p of the films were studied as functions of thickness. The reduction of t causes the decrease of the Curie temperature T-C in addition to the increase of p of the films. Compared with the compressive strain in the La0.67Ca0.33MnO3/LaAlO3 films I the tensile strain in the La0.67Ca0.33MnO3/SrTiO3 films causes a faster reduction of T-C with t, and a larger value of rho(0). The low-temperature rho is found to follow well rho = rho(0) + Bomega(s)/sinh(2) (homega(s)/2k(B)T) + CTn, with rho(0) being the residual resistivity. The second term arises from the scattering by a soft optical phonon mode, and the third term denotes the other possible transport mechanisms. B, omega(s) ( the frequency of a soft optical mode) and C are fitting parameters. At temperatures higher than T-C, rho of all the films show activated conduction with rho = DTexp(E-a/k(B) T). Here, E-a is the activation energy. Based on the investigation of rho(0), omega(s) and E-a,E- the thickness and strain effects in the films are discussed, separately. Further study shows that the variation of T-C is mainly associated with E-a and omega(a), confirming the crucial role of the electron-phonon coupling in the strain effects on T-C.

We present the results of the Austin-Model 1 (AM1) geometry optimizations aimed at determining the charged geometry properties of -(PA)4-(PPP)m-(PA)4- triblock copolymers that have the well-barrier-well structure. The distributions of the doped charges depend upon the density of doped charges and the length of the barrier.

Polarons and bipolarons in mixed halide MX compounds were studied in the frame work of the two-band extended Peierls-Hubbard model.Different from the isolated MX chains,it was found that the segments tend to select impurities in mixed halide compounds.Then the charge confinement and the effect of electron-electron interactions were investigated.Finally the properties of impurities in mixed halide compounds with spontaneous charge transfer were also discussed.

We present a model calculation,using the tight-binding approach,of a one-dimensional heterostructure consisting of regular alternation of two different halogen-bridged transition-metal compounds (MX compounds).Superlattice and multi-quantum-well properties can be detected depending on the well-barrier alternation sequence.We prove the possibility of developing new multi-quantum-well devices based upon MX compounds.

In our calculations of lattice vibration, one acoustic and three optical branche s were found to compose the phonon vibrating spectrum. Some isolated modes with frequencies lying outside the continuum branches aise under the defect states. These localized modes result in the sharp peaks in the infrared absorption and Raman spectra.

Intrinsic charge transfer in mixed halide compounds PtXxX′1-x was studied in the framework of the two-band extended Pielerls-Hubbard model. It was found that the number of transferred charges can be a fraction times of the electronic charge. The maximum amount of transferred charges occurs at a certain x for a given mixed compound.

Magnetic properties and giant magneto-impedance (GMI) effects of Fe73.5Cu1Nb3Si13.5B9 single layered films and sandwiched fimls using Cu or Ag as the central layer prepared by radio frequency sputtering are investigated. The as-deposited single layered films are in amorphous state. The domain structures of single layered films annealed as 380℃ show that the films are in nanocrystalline state with homogeneous magnetization. The samples possess excellent soft magnetic properties and have the maxiumum values of GMI effects, the maxiumum GMI ratios are 18% and 14% in longitudinal and transverse fields, respectively, at 13MHz. Sandwiched films in the as-deposited state possess large GMI effects, the maximum GMI ratios of sandwiched films with a Cu central layer are 32% and 11% for longitudinal and transverse cases, respectively, and those of sandwiched films with a Ag central layer are 47% and 57% for longitudinal and transverse cases, respectively. Sandwiched films using Cu as the inner layer annealed at 250℃ exhibit large magneto-inductance effect at low frequencies. The maximum magneto-inductance ratio is 1733% at 100kHz.

Spin density wave in organic ferromagnets with open ends was studied and the results were compared with that in a closed organic ferromagnet ring. It was found that an end-open chain structure is unfavorable for the formation of the ferromagnetic ground. The competition of electron-electron interactions and the π-electron-radical spin couplings and their different effect on the SDW in the main chain were discussed.

A tight-binding model for conducting polymer poly(phenylene vinylene) (PPV) has been suggested in the framework of one-dimensional chains. The calculations showed that this model is effective to describe the ground state, polaron and bipolaron excitations in PPV. The stability of polarons and bipolarons was discussed by considering the effect of the dimensions, e-ph and e-e interactions.

The stabilities of one-dimensional conducting polymer chains with finte lengths have been studied in the frame work of the SSH tight-binding model.Three kinds of boundary conditions have been proposed to stabilize the dimerized structure of the chains.It was found that the natural boundary condition or the end-fixed boundary condition is applicable for getting a result to fit the observed photo-absorption of polyacetylene with short (N

Two series of [Pd/Co-Nb/Pd/Si] multilayer films were prepared by rf sputtering. The measurements of structure and magnetism were made by X-ray diffraction and magnetometer, respectively. As the thickness of Pd layers increases, the structure of Pd layers transfers from an amorphous state to a polycrystalline state. The polycrystalline state of the Pd layers shows two adjacent Pd fcc(111) peaks, which originate from the differences of lattice-mismatching degree and polarization of Pd atoms between the interfaces of Co-Nb layers and Pd layers and the interfaces of Pd layers and Si layers. As the thickness of Pd layers increases, the saturation magnetization monotonously increases from a value which is smaller than that of the bulk Co-Nb alloy with the same compositions to another value which is larger, then takes a constant value. This is contributed to the effects of polarization of Pd layers, dimension of Co-Nb magnetic layers and interdiffusion of atoms in the interfaces. The amorphous Co-Nb layers can influence the polarization of Pd atoms in the range of 2.5nm from the interfaces of Co-Nb layers and Pd layers. The is related to the strong interdiffusion of atoms in the interfaces and the large change of the Pd lattice constant in the film normal.

Based on the phenomenological theory of Camley and Barnas and coworkers (C-B), the dependence of magnetoresistance in Fe/Cr multilayers on the applied magne-tic field is calculated. In these multilayers an antiferromagnetic coupling exists between any two adjacent Fe-layers. The applied magnetic field is either parallel or perpendicular to the layers. Good agreement of the calculated results with the experimental ones is found. The symmetry implicitly involved in the C-B theory is disclosed and is used to simplify the original C-B formalism, this leads to the closed expressions for the distribution function of conducting electrons and for magnetore-sistance.

With a local potential of site-impurity in the frame work of the SSH model, the Coulomb effect of the dopant ions on the vibrational modes around the charged-soliton in doped poly-acetylene has been studied. The calculated results showed that the Goldstone theorem will be destroyed and the translation mode g1 will be pined by the dopant potential. At the same time, a new even-parity mode g′ 1 has been found. The appearance of g1 and g′1 interpret well the broad peak at 930 cm-1. In addition, other localized modes have also been discussed.

The stability of soliton pairs and the electronic energy level structures in a doped poly-acetylene chain have been studied under natural boundary conditiono. In the Itamiltanian usel an end point potential was added to the SHH model, and the screened Coulomb potential of impurities and e-e interaetion on the tattice points were also indndelincluded. The caleulated results Show that, as the range of coulomb interaction is long enongh, stable soliton pairs are formel in the chain, and the stability is enlanced by the influce of the ends the gap width becomes narrow with the increase of chain length. But the deplndence of transition energg from soliton level to band bottom on chain length is not very signicant.

Based on the fact of the existance of a small amount itinerant electrons, a new theoretical model giving rise to magneto-crystalline anisotropy in compound Nd2Fe14B is presented in this paper. It is proposed that a combined effect on Nd-ion coming from both the crystal field of ligands and the electric field of itinerant electrons results in the anisotropy in the compound. An approach of calculating the interaction between itinerant electrons and central Nd-ion is given. The magneto-crystalline anisotropy of Nd-ion and its temperature dependences are calculated based on the model. The results are in good agreement with the experiments, and also give explanation to the spin reorientation phenomenon in the compound.