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1.
R. A. Ganeev A. I. Ryasnyanskii M. K. Kodirov Sh. R. Kamalov V. A. Li R. I. Tugushev T. Usmanov 《Technical Physics》2002,47(8):991-995
Nonlinear optical parameters (nonlinear refractive indices and nonlinear absorption coefficients) of solutions of polyvinylpyrrolidone doped by cobalt to various concentrations are measured at the lasing and second-harmonic wavelengths of a picosecond Nd:YAG laser (λ=1064 and 532 nm, respectively, and τ=35 ps). Data on optical limitation in these solutions are presented. The absence of nonlinear absorption in the IR spectral range and its significant effect in the visible range are demonstrated. Optical limitation at a wavelength of 1064 nm is related to defocusing, whereas at 532 nm, this effect is caused by two-photon absorption and partially by inverse saturated absorption and defocusing. Nonlinear optical parameters of metal-polymer complexes are reported. 相似文献
2.
A model is proposed for magnetic ordering in Fe/Cr-type multilayers substantially above the Néel temperature of bulk chromium. Redistribution of the charge (and, hence, spin) density near the Fe/Cr interfaces gives rise to the formation of an essentially inhomogeneous spin-density-wave (SDW) state in the chromium spacer. The spatial structure of the antiferromagnetic order parameter in thick spacers is described. The SDW contribution to the effective exchange coupling between the moments in adjacent iron layers is calculated. The data obtained are used in the interpretation of experimental data on the tunneling spectroscopy of trilayers and neutron diffraction from Fe/Cr superlattices. 相似文献
3.
JETP Letters - We calculate the photoionization cross section of a molecular endohedral that denote as M@CN. We limit ourselves to diatomic molecules. The consideration is much more complex than... 相似文献
4.
A mechanism of the interlayer exchange coupling in layered structures of the Fe/Cr(001) type with rough interfaces is proposed. The theory is based on a model of the charge-induced spin density wave (SDW) formed in the chromium layer. It is shown that the effective magnetic coupling between thick ferromagnetic layers arises due to variations of the SDW vector orientation in the antiferromagnetic layer over a characteristic length ζ determined by the exchange stiffness of chromium. A general expression for the effective magnetic coupling energy E(ψ) as a function of the angle ψ between magnetic moments of the ferromagnetic layers is obtained and numerically analyzed for an arbitrary value of the parameter ρζ, where ρ is the density of monoatomic steps on the interface. For ρζ?1, the form of E(ψ) is typical of a model with the “ biquadratic” interaction, while in the case of ρζ?1, the dependence obtained differs significantly. The proposed mechanism is used to interpret the results of measurements of the interlayer exchange coupling in Fe/Cr(001) structures. 相似文献
5.
An Anderson model with N-fold degeneracy in the Kondo regime is considered. It is presumed that the electron-electron correlations in the system of
f electrons have their maximum strength. A criterion for instability against the formation of a weakly antiferromagnetic phase
superposed on the Kondo state is obtained by the auxiliary-boson method using the 1/N expansion. An effective interaction leading to the formation of magnetic ordering appears because of the spin fluctuations
in the system of localized electrons. The phase diagram of the system is constructed.
Zh. éksp. Teor. Fiz. 111, 600–614 (February 1997) 相似文献
6.
A model of noncollinear magnetic ordering in Fe/Cr-type multistructures was suggested. The model was based on the idea of
charge (and, as a consequence, spin) density redistribution near a metal-metal interface. A peculiar state of the whole structure
characterized by strong short-range antiferromagnetic ordering in the interlayer and a pronounced dependence of magnetic characteristics
on the properties of the boundary between iron and chromium layers was shown to be formed in a certain temperature range.
Inhomogeneous antiferromagnetic structures with a vector order parameter were found, and the effective exchange coupling between
neighboring iron layer moments was calculated using the Ginzburg-Landau expansion of the thermodynamic potential. The results
were used to discuss the experimental data on Fe/Cr superlattices obtained in neutron scattering and magnetization measurements. 相似文献
7.
V. N. Men’shov V. V. Tugushev S. Caprara 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(3):337-343
We discuss a possible route to explain high-temperature ferromagnetism
in Si:Mn dilute magnetic semiconductors. We argue that most Mn atoms are
segregated within nanometer-sized regions of magnetic precipitate and form
the alloy, or compound, MnSi2
-z
with z
≈ (0.25?\div0.30), whereas
a small minority of Mn atoms forms ?ngstr?m-sized magnetic defects
embedded in the host. Assuming that MnSi2
-z
is a weak itinerant ferromagnet
which supports sizable spin fluctuations (paramagnons) far above the
intrinsic Curie temperature, we show that the Stoner enhancement of the
exchange interaction between the local magnetic moments of the defects occurs. As
a result, a significant increase of the temperature of global
ferromagnetic order in the system is achieved. We develop a phenomenological
approach, to qualitatively describe this effect. 相似文献
8.
R. A. Ganeev G. S. Boltaev R. I. Tugushev T. Usmanov 《Applied physics. B, Lasers and optics》2010,100(3):571-576
We present the results of studies of the nonlinear optical properties of Pd, Ru, and Au nanoparticles. We studied the nonlinear
refraction and nonlinear absorption of suspensions of these nanoparticles at 1064-nm wavelength. A relatively strong nonlinear
absorption of the Pd nanoparticles was observed in the case of 1064-nm, 50-ps pulses (β=2×10−9 m W−1). The Ru and Pd nanoparticles showed weak negative nonlinear refraction (γ∼−(6–8)×10−16 m2 W−1) in this spectral range. In the case of the Au nanoparticles, a saturated absorption at 532 nm dominated over other nonlinear
optical processes. 相似文献
9.
A. A. Titov E. T. Kulatov Yu. A. Uspenskii V. V. Tugushev H. Mariette J. Cibert 《Bulletin of the Lebedev Physics Institute》2008,35(2):57-62
The X-ray K spectra of Mn absorption were used for Mn ion distribution in (Ga, Mn)N. According to the performed calculations, two threshold lines were observed in the K spectra of (Ga, Mn)N crystals with uniform Mn ion distribution. If Mn ions form chains, these two threshold lines merge into one broad line. 相似文献
10.
A model is proposed for exchange coupling between ferromagnetic metal layers through a nondegenerate semiconductor interlayer with point defects. The asymptotics of the exchange integrals is calculated. It is shown that the interlayer exchange can reverse sign depending on the position and occupation of impurity states in the interlayer. The results provide a qualitative explanation of the experimental data obtained for iron/silicon multilayers. 相似文献