Ling-Yun Zhang

Hole-mediated ferromagnetic enhancement and stability in Cu-doped ZnOS alloy thin films

We report room temperature ferromagnetism enhancement of Cu-doped ZnOS (Zn1−xCuxO1−ySy) alloy thin films with high hole concentration. The Zn0.91Cu0.09O0.92S0.08 alloy thin films with a hole concentration of 4.3xa0×xa01019xa0cm−3 show the strongest magnetization of 1.5μB/Cu. First-principles calculation shows that high hole concentration stabilizes the ferromagnetic ordering in the Zn1−xCuxO1−ySy system, indicating a strong correlation between ferromagnetic stability and hole concentration. These results suggest that the Zn1−xCuxO1−ySy alloy with high hole concentration is promising to find applications in spintronic devices.

Stretching vibration influence of the hydrogen bond on a localized excitation and thermodynamic properties of DNA double helices

The propagation of a localized excitation and the thermodynamic properties in DNA double helices due to stretching vibration of hydrogen bond are discussed. The stretch of the hydrogen bonds is considered as a nonlinear chain with cubic and quartic potential. The analytic solution of the solitary wave is obtained by using the continuum approximation and its stability has been discussed. With the help of the thermodynamic Green function technique, the temperature and anharmonicity effects on the thermodynamic properties of DNA are investigated. The theoretical calculation of the specific heat in DNA at low temperature is consistent with the experimental result. The numerical simulation of the differential-difference equation shows that the solitary wave is pinned by the lattice. It is also pointed out that the conformational transitions from B-DNA to A-DNA can occur in the case of asymmetry potential with quartic term

Thermal properties of high temperature superconductors: Soliton statistics approach

We develop a soliton statistics approach to discuss the lattice effect of high temperature superconductor in the Davydov model on the basis of the bisoliton idea. We prove that lattice displacement in the Davydov model satisfies ϕ4 field form. Critical temperature of high temperature superconductor is studied from statistics of lattice kink. We have shown that the lattice effect is pronounced for thermal properties of high temperature superconductors. Comparision between theoretical and experimental results are good agreement for LaSrCuO and YBaCuO superconductor materials.

Quantum fluctuations of thermal transport coefficients in mesoscopic systems

The quantum interference effects in small-size samples are discussed. Using: a corrected Wiedemann-Franz law, we obtain the functional dependence of the relative thermal conductivity on the relative electrical conductivity. The results show that the fluctuations of thermal transport coefficients have a periodic oscillation corresponding to the electrical conductivity fluctuation, but the amplitudes of them are different for different materials

Hubbard effect on soliton motion of polyacetylene

By starting with the antiferromagnetic chain model, it has been set up that the coupled nonlinear equations describe the interaction between the lattice displacement and the electronic wave function. We obtain an analytic solution of the equation of motion and study the nonlinear dynamics of polyacetylene by considering the Hubbard interaction. The influence of the Hubbard potential upon the parameters of the soliton such as the effective mass and hall-width of the lattice kink has been revaluated. With increasing Hubbard potential, the dimerization and half-width will increase bur the effective mass will decrease.

Magnetization configuration and potential dependence of giant magnetoresistance in magnetic multilayers

The angular and potential dependence of giant magnetoresistance in magnetic multilayers is discussed. The functional dependence of the giant magnetoresistance on magnetic configuration variation is obtained by considering both interface and bulk magnetization contributions. The results show that the giant magnetoresistance in magnetic multilayers varies with magnetization angle and differs for different layer thicknesses. We also clarify the interface and bulk contribution of the giant magnetoresistance in magnetic multilayers for various exchange potentials and impurity scattering potentials.

Correlation between the potential contribution and magnetic transport properties for magnetic multilayers

We discuss the exchange potential and impurity scattering potential effect on the magnetic transport properties of magnetic multilayers. In the case of Hartree-Fork approximation, the model Hamiltonian with respect to the magnetization and potential contribution is presented. The expression of giant magnetoresistance is obtained by considering both interface and bulk magnetization contribution. The results show that the giant magnetoresistance in magnetic multilayer is different for different layer thickness. Meanwhile, we also clarify the interface and bulk contribution of the giant magnetoresistance in magnetic multilayer for different exchange potential and impurity scattering potential.

Giant Magnetoresistance in Magnetic Multilayers: Dependence on Temperature and on Layer Thickness

We considered that the d band in transition metals plays a special role in gain magnetoresistance. It is confirmed that an asymmetric density of states at the Fermi surface is important to result in giant magnetoresistance. The expression of giant magnetoresistance has been obtained by considering the spin splitting of the electron energy band. We built the free energy in the magnetic multilayers and found that the electron-phonon interaction can have an important effect on the spin splitting of the electron energy band in jellium-like models. Numerical calculations using our approach demonstrate the agreement between experimental and theoretical values.

The Effect of the Electron–Phonon Interaction on Giant Magnetoresistance in Magnetic Multilayers*

We built electron and phonon free energies and attempted to investigate the effect of the electron–phonon interaction on giant magnetoresistance in magnetic multilayers. Starting from a jellium-like model, we found that the electron–phonon interaction can have an important effect on the spin splitting of electronic energy band. The expression of giant magnetoresistance has been obtained by considering the spin splitting of electronic energy band, indicating that the effect of phonon could not be neglected. Numerical calculations using our approach demonstrate the agreement between experimental and theoretical values.