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1.
Thin films of Ti1−xCoxO2 (x=0 and 0.03) have been prepared on sapphire substrates by spin-on technique starting from metalorganic precursors. When heat treated in air at 550 and 700 °C, respectively, these films present pure anatase and rutile structures as shown both by X-ray diffraction and Raman spectroscopy. Optical absorption indicate a high degree of transparency in the visible region. Such films show a very small magnetic moment at 300 K. However, when the anatase and the rutile films are annealed in a vacuum of 1×10−5 Torr at 500 and 600 °C, respectively, the magnetic moment, at 300 K, is strongly enhanced reaching 0.36μB/Co for the anatase sample and 0.68μB/Co for the rutile one. The ferromagnetic Curie temperature of these samples is above 350 K. 相似文献
2.
N.L. Tsintsadze P.K. Shukla L. Stenflo 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):109-115
The electroweak coupling between intense neutrino beams and strongly degenerate relativistic dense electron-positron magnetoplasmas
is considered. The intense neutrino bursts interact with the plasma due to the weak Fermi interaction force, and their dynamics
is governed by a kinetic equation. Our objective here is to develop a kinetic equation for a degenerate neutrino gas and to
use that equation to derive relativistic magnetohydrodynamic equations. The latter are useful for studying numerous collective
processes when intense neutrino beams nonlinearly interact with degenerate, relativistic, dense electron-positron plasmas
in strong magnetic fields. If the number densities of the plasma particles are of the order of 1033 cm-3, the pair plasma becomes ultra-relativistic, which strongly affects the potential energy of the weak Fermi interaction. The
new system of equations allows several neutrino-driven streaming instabilities involving new types of relativistic Alfvén-like
waves. The relevance of our investigation to the early universe and supernova explosions is discussed.
Received 11 September 2002 Published online 4 February 2003
RID="a"
ID="a"Permanent address: Department of Physics, Tbilisi State University, Chavchavadze 3, Tbilisi 38028, Georgia.
RID="b"
ID="b"Also at the Department of Plasma Physics, Ume? University, 90187 Ume?, Sweden; and the Center for Interdisciplinary Plasma Science,
Max-Planck Institut für Plasmaphysik und extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany. e-mail: ps@tp4.ruhr-uni-bochum.de
RID="c"
ID="c"Permanent address: Department of Plasma Physics, Ume?University, 90187 Ume?, Sweden. 相似文献
3.
N. Stevanović D. Nikezić 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(3):397-406
Collision of swift ions with atoms was considered in this paper. The
projectile and target atoms were modeled as assemblies of quantum
oscillators and it was assumed that both, target and projectile could be
excited or ionized, without charge exchange. The model presented here is an
extension of the one given by Sigmund and Haagerup [Phys. Rev. A 34, 892 (1986)]. The number of electrons bound to the projectile, as a function of the projectile velocity,
was used from Cabrera-Trujillo et al. [Phys. Rev. A 55, 2864 (1997)]. Contributions to energy loss from excitation of the projectile and targets were separately considered. It
has been found that projectile excitation contributes up to 20% to the
total energy loss in the lower energy region. Comparisons with other
authors, including SRIM 2003, are also given and good agreement was found. 相似文献
4.
Sergey E. Zirka Yury I. Moroz Philip Marketos Anthony J. Moses 《Journal of magnetism and magnetic materials》2008
The loss predictive methods based on the static and dynamic components of power loss are compared with the methods where the total loss is subdivided into hysteresis, classical and excess components. It is explained why the simplest two-component methods can be preferable. An approach to the characterization of a given steel is outlined. 相似文献
5.
Isothermal decomposition behavior of the high nitrogen concentration γ-Fe[N] prepared from pure iron
The isothermal decomposition characteristic of the homogeneous high nitrogen austenitic samples prepared by a new multi-stage nitriding process was investigated by SEM and TEM in this paper. Lamellar-structure precipitations arranged on the decomposed austenite grain boundaries (GBs) and the flaky γ′ particles and network-structure precipitations appeared inside of the γ matrix. The extra high Vickers hardness more than 800 HV was found in the 5-h aged samples, which was different from those of the bainitic/martensitic structures in Fe-C alloys. The SAED analysis indicates the γ′ has the coherent relation with the parent γ-Fe[N] phase and the interstitial nitrogen atoms are inclined to aggregate on {1 1 0}γ′/γ planes, which also contributes to the hardness of the matrix. 相似文献
6.
P. Thangadurai S. Ramasamy R. Kesavamoorthy 《Journal of Physics and Chemistry of Solids》2005,66(10):1621-1627
Nanocrystalline tin oxide (SnO2) was prepared by chemical precipitation method with different grain sizes. The X-ray diffraction studies showed the structural stability of nanocrystalline SnO2 under high-pressure. Electrical and dielectric properties were studied on these samples using complex impedance spectroscopy under different hydrostatic pressures. Electrical resistivity and dielectric studies showed a transition in nanocrystalline SnO2 when it was subjected to high-pressure. The transition pressures obtained from both the resistivity and dielectric measurements agree with each other. The transition pressures were found to increase considerably with the decrease in grain size. Dielectric constant was found to decrease with the reduction of grain size. In order to find whether the transition with pressure is structure- related or not, Raman spectroscopy was done at normal temperature and pressure (NTP) and as a function of pressure at room temperature. Raman modes at NTP showed lines which correspond to tetragonal rutile structure of SnO2. In situ high-pressure Raman measurements were carried out up to 3.38 GPa. No structural change was found with pressure. 相似文献
7.
Within a large class of exact solutions of the Einstein equations describing a black hole embedded in a Friedmann universe it is shown that, under certain assumptions, only those with comoving Hawking–Hayward quasi-local mass are generic, in the sense that they are late-time attractors. 相似文献
8.
Surfaces of GaN films were investigated by atomic force microscopy (AFM) with implemented piezoelectric force microscopy technique. A model of PFM based on the surface depletion region in GaN films is discussed. The local piezoelectric effect of the low frequency regime was found to be in phase with the applied voltage on large domains, corresponding to a Ga-face of the GaN layer. Low piezoresponse is obtained within the inter-domain regions. The use of frequencies near a resonance frequency enhances very much the resolution of piezo-imaging, but only for very low scanning speed the piezo-imaging can follow the local piezoelectric effect. An inversion of the PFM image contrast is obtained for frequencies higher than the resonance frequencies. The effect of a chemical surface treatment on the topography and the piezoresponse of the GaN films was also investigated. Textured surfaces with very small domains were observed after the chemical treatment. For this kind of surfaces, piezo-induced torsion rather than bending of the AFM cantilever dominates the contrast of the PFM images. A small memory effect was observed, and explained by surface charging and confinement of the piezoelectric effect within the carrier depletion region at the GaN surface. 相似文献
9.
F. Frontera A. Basili D. Dal Fiume T. Franceschini G. Landini E. Morelli J. M. Poulsen S. Silvestri E. Costa D. Cardini et al. 《Il Nuovo Cimento C》1990,13(2):437-444
Summary The LAPEX payload is described in the configuration that will be launched to observe the supernova SN 1987A. The balloon flight
will be performed from Alice Springs (Australia) in April 1989 as a part of a NASA balloon campaign. The experiment will allow
simultaneous observations of source and background in order to minimize systematic errors due to background variations. The
limiting flux sensitivity of the instrument in the (20÷200) keV energy band is 4·10−6 ph/(cm2s keV) or ∼2.5 mCrab for a 104 s observation of SN 1987A. The presence of a57Co emission line in the SN 1987A photon spectrum could be detected down to an intensity level of ∼8·10−5 photons/cm2s as at 99.7% confidence level. The high resolution of the event timing (<0.1 ms) will make it possible to detect millisecond
pulsations with amplitudes down to ∼4% of the expected average flux from SN 1987A in the (20÷60) keV band.
To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee. 相似文献
10.
We study the non-spherical gravitational collapse of the strange quark null fluid. The interesting feature which emerges is that the non-spherical collapse of charged strange quark matter leads to a naked singularity whereas the gravitational collapse of neutral quark matter proceeds to form a black hole. We extend the earlier work of Harko and Cheng [Phys. Lett. A 266 (2000) 249] to the non-spherical case. 相似文献