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Homogeneous amorphous MnxGe1-x:H films were synthesized under thermal nonequilibrium condition by magnetron co-sputtering technology with hydrogen in Ar atmosphere. Compared to the MnxGe1-x films without hydrogen, the MnxGe1-x:H films with hydrogen show higher concentration of hole carriers, larger conductivity, and higher saturation magnetization. Moreover, it was found that the anomalous Hall resistivity is proportional to the perpendicular magnetization. These electrical and magnetic properties indicate that the ferromagnetism of the MnxGe1-x:H films is intrinsic ferromagnetism mediated by the spin-polarized hole carriers. [ABSTRACT FROM AUTHOR]

We theoretically investigated the electronic structures and magnetic properties of (Mn,C)-codoped ZnO system based on the first-principles calculations within a GGA+Up,d approach. We found that codoping C is a promising approach to enhance the ferromagnetic coupling between the nearest-neighboring Mn ions due to the strong hybridization between the C:2p and the Mn:3d states. Moreover, the spin-polarized states induced by C are so extended that they can mediate long-ranged ferromagnetic exchange interactions beyond the nearest-neighboring case. Therefore, (Mn,C)-codoped ZnO is expected to be a ferromagnetic semiconductor with long-ranged ferromagnetism and high Curie temperature. [ABSTRACT FROM AUTHOR]

Amorphous Ge1-xMnx magnetic semiconductor films with high Mn concentrations were prepared on liquid-nitrogen (LN2)-cooled glass substrates by ultrahigh vacuum thermal coevaporation. Hysteresis loops measured at 5 K show coexistence of ferromagnetism and paramagnetism. The maximum Curie temperature of 220 K was found in Ge0.48Mn0.52 film. Moreover, exchange bias occurs in magnetization hysteresis loops for samples with higher Mn concentrations, which can be explained by the antiferromagntic exchange coupling between ferromagnetic phase and antiferromagnetic phase. All the Ge1-xMnx magnetic semiconductor films show semiconducting transport behavior and anomalous Hall effects below the Curie temperature, indicating carrier-mediated ferromagnetism. [ABSTRACT FROM AUTHOR]

The effect of atomic disorder or chain length on the stability of photoinduced polarization inversion has been studied. The atomic disorder was simulated by square-random or Gaussian-random model. It was found that for the square-random distribution case, photoinduced polarization inversion remains steadily when atomic disorder is less than [FRACTION SHAPE="CASE"][NUM]1[/NUM][DEN]8[/DEN][/FRACTION]a (a is the lattice constant of polyacetylene), the reversion polarization disappears and gets into normal polarized state when the disorder is stronger than over [FRACTION SHAPE="CASE"][NUM]1[/NUM][DEN]8[/DEN][/FRACTION]a. The reason of a normal polarization resulted from the strong lattice disorder was discussed. The relationship between the reverse polarization of biexciton state and the confinement constant t[sub e] as well as the variation of chain length was also studied. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which prepared cobalt-niobium/palladium multilayers by radio frequency sputtering method. Experimental details; Results of low-angle x-ray diffraction; Conclusion.

The electrical transport of DNA is closely related to the density of itinerant pi electrons because of the strong electron-lattice interaction. The resistivities of two typical DNA molecules [poly(dG)-poly(dC) and lambda-DNA] with varied densities of itinerant pi electrons are calculated. It is found that the dependence of the resistivity on the density of itinerant pi electrons is symmetrical about the half-filling state of itinerant pi electrons in poly(dG)-poly(dC). At the half-filling state, the Peierls phase transition takes place and poly(dG)-poly(dC) has a large resistivity. When the density of itinerant pi electrons departs far from the half-filling state, the resistivity of poly(dG)-poly(dC) becomes small. For lambda-DNA, there is no Peierls phase transition due to the aperiodicity of its base pair arrangement. The resistivity of poly(dG)-poly(dC) decreases with increasing length of the molecular chain, but the resistivity of lambda-DNA increases with increasing length. The conducting mechanisms for poly(dG)-poly(dC) and a few lambda-DNA molecules with varied densities of itinerant pi electrons are analyzed.