Showing papers on "Saturation (graph theory) published in 1979"
TL;DR: A detailed experimental study of the susceptibility at the spin-glass transition in (Eu,Sr)S is presented in this article exhibiting a strong sensitivity of $\ensuremath{\chi}({T}{f})$ and ${T}_{f}$ to small external magnetic fields and different measuring frequencies.
Abstract: A systematic experimental study of the magnetic properties in insulating ${\mathrm{Eu}}_{x}{\mathrm{Sr}}_{1\ensuremath{-}x}\mathrm{S}$ is reported, giving evidence of spin-glass behavior for concentrations $0.13l~xl~0.5$ due to short-ranged exchange interactions with opposite sign. The magnetic properties below the spin-glass transition temperature ${T}_{f}$ are explored by low-field magnetization, ac susceptibility, and neutron-diffraction measurements. The magnetization and remanent magnetization are found to depend on the thermomagnetic history. An unusually pronounced maximum is observed in the thermoremanent magnetization as function of the previously applied field. The saturation values of the remanent magnetizations remain only a few percent of the saturation magnetizations, even for the high Eu concentrations. Their temperature, field, and time dependence are studied. Comparison is made with metallic spin-glass samples. A detailed experimental study of the susceptibility at the spin-glass transition ${T}_{f}$ in (Eu,Sr)S is presented exhibiting a strong sensitivity of $\ensuremath{\chi}({T}_{f})$ and ${T}_{f}$ to small external magnetic fields and different measuring frequencies. In an attempt to analyze the data, the distinction between the spin-glass phenomenon and superparamagnetism is stressed. Near the percolation threshold of the exchange interactions, ${x}_{p}=0.13$, a transition from spin-glass behavior to "pure" superparamagnetism is clearly observed in ${\mathrm{Eu}}_{x}{\mathrm{Sr}}_{1\ensuremath{-}x}\mathrm{S}$.
215 citations
TL;DR: In this article, high-energy ion scattering in combination with channeling has been used to study the W(001) + hydrogen surface and it has been shown conclusively that the clean W (001) and the clean H (H) surfaces are reconstructed at room temperature, that the surface reorders by H saturation, and that two models proposed for the $c(2
Abstract: High-energy ion scattering in combination with channeling has been used to study the W(001) + hydrogen surface. It is shown conclusively that the clean W(001) and the $\mathrm{W}(001)c(2\ifmmode\times\else\texttimes\fi{}2)\mathrm{H}$ surfaces are reconstructed at room temperature, that the surface reorders by H saturation, and that two models proposed for the $c(2\ifmmode\times\else\texttimes\fi{}2)$ surface structure are not valid. Furthermore we have obtained absolute coverage data [for the W(001) + ${\mathrm{D}}_{2}$ system] using a nuclear reaction technique.
120 citations
TL;DR: Two-dimensional computer simulations show that short-wavelength ion fluctuations and density-profile steepening are dominant factors in the saturation of the $2 √ √ ϵ ϵ −1 −2 ϵ -1 instability as mentioned in this paper.
Abstract: Two-dimensional computer simulations show that short-wavelength ion fluctuations and density-profile steepening are dominant factors in the saturation of the $2{\ensuremath{\omega}}_{\mathrm{pe}}$ instability. The long-term evolution of this instability is described and the implications of this complex saturation process for absorption and harmonic emission are discussed.
100 citations
TL;DR: Saturation of stimulated Brillouin scattering has been observed in the interaction of long-pulse C${O}}_{2}$-laser radiation with underdense hydrogen plasma at intensities of \ensuremath{le}${10}^{13}$ W/${\mathrm{cm}}^{2} as discussed by the authors.
Abstract: Saturation of stimulated Brillouin scattering has been observed in the interaction of long-pulse C${\mathrm{O}}_{2}$-laser radiation with underdense hydrogen plasma at intensities of \ensuremath{\le}${10}^{13}$ W/${\mathrm{cm}}^{2}$. The stimulated Brillouin scattering is strongly modulated with average long-time reflectivity approximately half the peak value. The maximum reflectivity measured was 60% and wave breaking is postulated as the principal saturation mechanism.
40 citations
TL;DR: Saturation of Brillouin backscatter is observed from underdense plasma targets with laser intensities as low as 2\ifmmode\times\else\texttimes\fi{}${10}^{11}$ W/${\mathrm{cm}}^{2}$ as mentioned in this paper.
Abstract: Saturation of Brillouin backscatter is observed from underdense plasma targets with C${\mathrm{O}}_{2}$ laser intensities as low as 2\ifmmode\times\else\texttimes\fi{}${10}^{11}$ W/${\mathrm{cm}}^{2}$. Maximum reflectivity is about 5%, implying an ion-wave amplitude of 1%. The most likely limiting mechanism is found to be ion trapping, which is effective at our low $\frac{{T}_{e}}{{T}_{i}}$ ratio.
34 citations
TL;DR: In this article, the capacitance of amorphous silicon films was measured at frequencies between dc and 10.7 Hz, and at temperatures between 150 and 400 K. At low frequencies the conductance was nearly independent of frequency, an exponential function of temperature, and influenced by contacts.
Abstract: The admittance $Y=G+j\ensuremath{\omega}C$ of amorphous silicon films, produced by electron-beam evaporation, has been measured at frequencies between dc and ${10}^{7}$ Hz, and at temperatures between 150 and 400 K. At low frequencies the conductance $G$ was nearly independent of frequency, an exponential function of temperature, and influenced by contacts. At medium frequencies $G$ increased almost proportionally to ${\ensuremath{\omega}}^{s}$, with $s\ensuremath{\simeq}0.9$. In this region $G$ was found to be contact independent and superlinearly dependent on temperature. In the high-frequency region a saturation behavior of $G$ was observed. The capacitance $C$ decreased monotonically from low to high frequencies. These measured properties have been attributed to a hopping between sites, randomly distributed in space and energy, and over the barriers separating the sites. The barrier height has been correlated to the intersite separation by assuming Coulomb-like potential wells. This model accounts both for the ${\ensuremath{\omega}}^{s}$ behavior and for the saturation of $G$. However, to obtain good agreement between theory and experiment it was necessary to envisage a minimum relaxation time ${\ensuremath{\tau}}_{o}$ not much smaller than ${10}^{\ensuremath{-}6}$ sec. In contrast, ${\ensuremath{\tau}}_{o}$ has in previous work been interpreted to be of the order of an atomic vibrational period (\ensuremath{\sim} ${10}^{\ensuremath{-}12}$ sec).
22 citations
TL;DR: In this article, the saturation of inter-valence-band absorption in high-intensity light with a wavelength near 10 µm was investigated and the saturation coefficient decreases with intensity in a manner closely approximated by an inhomogeneously broadened two-level model.
Abstract: We present a theory of the saturation of inter-valence-band absorption in $p$-type Ge by high-intensity light with a wavelength near 10 \ensuremath{\mu}m. The absorption coefficient decreases with intensity in a manner closely approximated by an inhomogeneously broadened two-level model. The saturation intensity is calculated as a function of excitation wavelength and temperature and found to be in good agreement with measured values.
16 citations
TL;DR: In this article, the magnetoresistance in quantized accumulation layers on the surface of ZnO was investigated and the main conclusion was that scattering centers with giant magnetic moments (around 100 Bohr magnetons) must be present.
Abstract: Results are presented of magnetoresistance in quantized accumulation layers on the ($000\overline{1}$) surface of ZnO. The measurements were performed at low temperatures $T(2\ensuremath{-}80 \mathrm{K})$ and very high surface electron densities [(0.7-7) \ifmmode\times\else\texttimes\fi{} ${10}^{13}$ ${\mathrm{cm}}^{\ensuremath{-}2}$]. The magnetoresistance was found to be negative over the entire studied range of magnetic induction $B$ (up to 60 kG). Its absolute magnitude increases quadratically with $\frac{B}{T}$ at low values of $\frac{B}{T}$ and tends to saturation at high $\frac{B}{T}$. A spin scattering model adapted to surface channels accounts very well for the experimental data. The main conclusion drawn is that scattering centers with giant magnetic moments (around 100 Bohr magnetons) must be present on the ZnO surface. Such giant moments may originate from ionic clusters in combination with the free electrons localized at and/or screening the charged clusters. A quantitative analysis of the data reveals also the presence of centers with much lower magnetic moments (around 10 Bohr magnetons).
12 citations