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11.
E. Chikoidze Y. Dumont H.J. von Bardeleben J. Gleize F. Jomard E. Rzepka G. Berrerar D. Ferrand O. Gorochov 《Applied Physics A: Materials Science & Processing》2007,88(1):167-171
ZnO:Mn thin films are grown by the metal organic chemical vapor deposition technique. Mn (x) varies in the 0<x<0.44 range.
Vegard’s law has been verified for the lattice parameters. Electron paramagnetic resonance (EPR) measurements prove the substitutional
incorporation of Mn2+ on zinc sites. The behavior of the EPR line width regarding temperature is discussed. All ZnO:Mn layers show antiferromagnetic
interaction and a J1/kB=-15 K effective exchange constant. The optical band gap of ZnO:Mn increases with the manganese concentration. Raman spectroscopy
reveals a Mn-related scattering band.
PACS 71.55.Gs; 75.50.Pp; 61.10.Nz; 76.30.Fc; 75.30.Et; 78.40.-q 相似文献
12.
T. Hansel J. Müller C. Falldorf C. von Kopylow W. Jüptner R. Grunwald G. Steinmeyer U. Griebner 《Applied physics. B, Lasers and optics》2007,89(4):513-516
Digital holographic shape measurements using femtosecond laser pulses are reported. For contouring of very fast moving objects,
the simultaneous generation of at least two spectrally separated ultrashort pulses is required. To deliver this particular
spectral signature at high pulse energies, a chirped-pulse Ti:sapphire laser amplifier was modified to emit two spectrally
separated pulses with energies above 1 μJ each. The wavelength separation of these pulses was adjustable within the 50 nm
gain bandwidth, cutting out two distinct wavelength peaks by a variable double-slit assembly in a prism sequence. A Michelson-type
interferometer was employed to perform the two-wavelength contouring. The phases of the holograms and the phase differences
are calculated numerically, which allow us to deduce the contour lines of the topology of the object. The suitability of the
light source for digital holography is demonstrated with contouring of stationary objects and the potential for high-speed
applications is indicated.
PACS 42.40.-i; 42.60.By 相似文献
13.
von Eynatten G. Ritter T. Bömmel H. E. Dransfeld K. 《Zeitschrift für Physik B Condensed Matter》1987,65(3):341-345
A new model is presented which explains well the dramatic decrease of the Mössbauer line intensities with raising temperatures for freely dispersed iron microscrystals. In contrast to other theories which consider mainly vibration to be responsible we discuss here the decrease in terms of large amplitude diffusive rotational or translational jumps of the particles. Such diffusive jumps lead — in agreement with the observation — to a strong reduction of the Mössbauer-intensity without broadening the line width in a noticeable way. The typical potential well for a diffusing particle in an equilibrium position is derived quantitatively to be 13 meV. The model might be important also for a new understanding of the dynamics of catalytic clusters either in contact with each other or with larger solid surfaces.Part of this work was supported by the DFG Sonderforschungsbereich 306, Konstanz 相似文献
14.
Gunhild U. von Oertzen 《Journal of Physics and Chemistry of Solids》2007,68(3):324-330
Ab initio density functional calculations (plane wave GGA, CASTEP) were performed to determine the effect of O deficiency on the electronic structure of rutile, TiO2. O deficiency was introduced through either the removal of O or the insertion of interstitial Ti atoms. At physically realistic concentrations of O vacancies in the rutile lattice (i.e. 25% and less) O deficiency results in the population of the bottom of the conduction band, the location of the Ti 3d orbitals in the pure structure, increasingly with increasing vacancy concentration. We propose that this could be confused with the formation and population of gap states especially where O vacancies occur in isolated positions in the lattice. In contrast, Ti interstitials introduce a defect state into the energy gap, without an overall reduction in the size of the energy gap. O vacancies result in a spin polarized solution, whereas Ti interstitials do not. 相似文献
15.
We investigate a new parallel all-optical clock recovery scheme based on heterodyne beats of an optical sideband-filtered signal. The oscillating clock signal is recovered when the filtered sideband is combined with a stable local oscillator. The filtering is performed with an optical resonator, which by nature provides possibility for multiwavelength operation. The local oscillator could be realized by a multiwavelength laser, whose emission wavelengths are injection seeded with carrier wavelengths of the input data. The output signal of such a configuration benefits from a reduced bit-pattern effect and a stable offset level. The sideband filtering is demonstrated for 23 simultaneous channels at 100 GHz DWDM grid, each hosting a data stream of 10 Gbit/s. 相似文献
16.
C. von Borczyskowski F. Cichos J. Martin J. Schuster A. Issac J. Brabandt 《The European physical journal. Special topics》2007,144(1):13-25
Optical spectroscopy in combination with wide field or confocal optical
microscopy enables the investigation of single quantum objects such as
organic molecules, II/VI semiconductor quantum dots and silicon nanocrystals.
They all have fluctuations of luminescence intensities on time scales longer
than μs in common. A comparison reveals that despite the large differences
of the nature of the respective quantum objects, the intensity fluctuations
are related to a slow ionisation process followed
by a trapping of the photoejected charge in the non-conducing environment.
Detailed aspects of the dynamics are controlled by the dielectric properties
of the matrix. 相似文献
17.
F. Schreiber M. Hoffmann O. von Geisau J. Pelzl 《Applied Physics A: Materials Science & Processing》1993,57(6):545-551
The conventional and photothermally modulated (PM) ferromagnetic resonance (FMR) of magnetostatic modes (MSM) in yttrium iron garnet (YIG) films have been investigated as a function of temperature. Approaching the ferrimagnetic transition at T
c=560 K a strong enhancement of the PM-FMR signal amplitude is observed which is accompanied by a change of the signal shape. The observations are discussed in the framework of a model that takes into account the temperature derivatives of those quantities that contribute to the high-frequency susceptibility. At temperatures still below T
c a paramagnetic line emerges. The MSM disappear in a state of finite magnetization which is explained on the basis of damping of the MSM being important in the vicinity of the magnetic phase transition. Additionally, frequency and power dependent measurements are presented and the imaging ability of PM-FMR is demonstrated. 相似文献
18.
19.
20.
H. H. von Borzeszkowski 《Annalen der Physik》1991,503(8):558-562
It is argued that, due to the cut-off lengths arising in Quantum General Relativity, R2 corrections of Einstein's theory cannot be interpreted as quantum corrections. 相似文献