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1.
The specific magnetic susceptibility of polycrystalline and powdered samples was measured between 77 °K and 570 °K. This dependence was interpreted in intrinsic range suggesting the susceptibility is given as a sum of contributions of the lattice G and of free carriers L. The temperature dependence of the lattice susceptibility G= G 0 +T was checked: G 0 =–2·35× ×10–7, =4·5×10–11. The contribution L enabled to check the effective mass of holes mh=0·25m0 suggesting memh.

Herrn A. Hrubý gilt mein Dank für die Vorbereitung des polykristallinen Ingots von CdGeAs2.  相似文献   

2.
The dynamics of ann-component vector spin glass with infinite range interactions are investigated near and above the Gabay-Toulouse (GT) line. The local transverse susceptibility T for 0 varies along the whole GT lineT c1 (H) as v , with a field and temperature independent critical exponentv=1/2. The longitudinal susceptibility L () remains analytic for all (T, H)T c1 (H), except for a cross-over fromv=1 tov=1/2 forH0 at the freezing temperatureT=T f . The dynamic susceptibilities T () and L () are already coupled above the GT line via self-energy terms. BelowT c1 (H), this coupling is strongly enhanced by other mechanisms.  相似文献   

3.
The contact process is a model of spread of an infectious disease. Combining with the result of ref. 1, we prove that the critical exponents take on the mean-field values for sufficiently high dimensional nearest-neighbor models and for sufficiently spread-out models with d>4:() c as c and ()( c)–1 as c, where () and () are the spread probability and the susceptibility of the infection respectively, and c is the critical infection rate. Our results imply that the upper critical dimension for the contact process is at most 4.  相似文献   

4.
On the basis of the experimental reports, the mechanism of the second-order susceptibility (2) for the thermal/electric field poling of fused silica is analyzed, and expressions for (2) are detailedly derived and numerically calculated for the first time. By comparison the theoretical value of (2) with the experiment results, we propose that the effective (2) is created via both the interaction of the intense electric field with the third-order susceptibility (3) and the dipole orientation. The theoretical results show that, in the differently applied voltage, the dipole orientation and (3) play different role in the formation of (2). This theory successfully explains some experiment results.  相似文献   

5.
Let t be an analytic solution of the Schrödinger equation with the initial condition . Let t be the solution of the Schrödinger equation with the initial condition =, where is an analytic function. When 0, then t (x) t (x)1 ( t (x)), where t (x) trajectory starting from x. We relate this result to Feynman's sum over trajectories and complex stochastic differential equations.  相似文献   

6.
We have studied the various nonlinear optical processes that can be described by a fourth-rank (3)-tensor: signals of frequency in degenerate four-wave mixing (DFWM), harmonics of frequency 2 and 3, and (3)-type difference-frequency generation (DFG) with observation of anti-Stokes emission of a signal of frequency 212. Structural information in terms of normalized anisotropies is derived in all frequency domains by analysis of the elements of the respective orientation-dependent susceptibility tensor. A novel laser-based technique for the remote orientation analysis of crystalline structures is introduced.  相似文献   

7.
The empirical Cole-Cole and Cole-Davidson expressions for the -relaxation part of the susceptibility (z)=o/[z b +1] a are analyzed within a general framework of diffusion processes. It is found that (z) represents a Green function for such a process, and the corresponding relaxation function can be expressed in terms of a local time processF(t)=1–E 0[(t)]. This latter process describe an intermittent relaxation process occurring on a Cantor like visiting time-setJ o. The exponentsa andb are fractal dimensions of such sets. It is argued that, in caseb1, the underlying diffusion process is related to the experimentally observed -process which then triggers the -process on the time-setJ o.  相似文献   

8.
A simple quark pair creation model is introduced to study exclusive decays of {c_J} into baryon-antibaryon pairs. With this simple model, some exclusive decay processes, for example, {c0} B¯ (B = ,0,-) are investigated and their decay widths are evaluated by inclusion of the properties of outgoing baryons, and the results show that the strengthened decay channels {c_J} ¯(J = 0, 2) are easily understood by considering only the color singlet contribution of P-wave charmonium.  相似文献   

9.
The dependence on angle is considered for the hysteresis-free initial susceptibilities a and ar together with the initial susceptibility o for iron and nickel aerosol powders, as well as the effects on these characteristics from changes in powder packing density. Estimates are made of the negative-interaction fields, and a quantitative comparison is made between the observed ar() and theoretical values by means of the pair model. The correlation between the experimental and theoretical relationships confirms the concepts used on the predominant effects from magnetostatic interaction in the mechanism for magnetization reversal in powders of materials with low anisotropy.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, pp. 40–43, July, 1984.  相似文献   

10.
A relation between the magnetic susceptibility(k, ) of an interacting 1-D Fermi system and the dielectric function(q) of a 2-D Coulomb gas is established. By applying a cluster-expansion technique and by using known results for the pair-correlation function of the Coulomb gas we obtain a number of expressions for(q) which apply in different regions of theq-plane and in different temperature intervals. These results supplement the existing picture of the transition from non-metallic to metallic behaviour occurring in the 2-D Coulomb gas as the temperature increases. The relation between(q) and(k, ) is then used to derive explicit expressions for(k, ) from these results for(q). The change in the dielectric response of the 2-D Coulomb gas is reflected by a change in the magnetic response of the 1-D Fermi system: as a function of the spin non-flip coupling constant the susceptibility of the Fermi system changes from normal paramagnetic behaviour to non-magnetic behaviour characteristic of a bound singlet-spin ground state, as decreases. Our result for the gap in the spin excitation spectrum of the Fermi system is in agreement with the results of other authors.On sabbatical leave from Institut für Theoretische Physik, TU Hannover, GermanyWork at U.C.S.B. supported in part by the National Science Foundation  相似文献   

11.
In this paper, A novel wavelength divison multiplexing (WDM) nets is proposed by use of cascaded second-order nonlinearities ((2):(2)) in the D-fiber grating after periodically thermal/electric-field poling, and is theoretically analyzed for the first time. The coupled mode equations of the (2):(2) nonlinearities are derived, and the analytic expressions for the electric-field amplitude of converted light wave and the conversion efficiency are obtained under the small signal approximation, which are well consistent with numerical calculations. Both analytic expressions and numerical results show that, under the phase matching, is proportional to the logarithm of the square of pump light power, and the 4th power of the grating length L and the second-order nonlinearity d. The calculated results also show that and of this fiber grating can be reached over -17dB and 120nm, respectively. With the increase of L, increases rapidly while decreases quickly. The results of simulated calculations and theoretical analysis show that the cascaded (2):(2) process is different from quasi-phases-matched difference-frequency generation.  相似文献   

12.
The Faraday method is used to study for the first time the temperature dependence of the magnetic susceptibility of intermetallic compounds of rare-earth metals (REM = Gd, Dy, Ho, and Er) with aluminum in a wide temperature interval from room temperature to 1700°C encompassing their solid state, melting process, and liquid state. It is established that for all examined compounds, except the Gd–Al system, the dependence (T) is linear. It is described by the modified Curie–Weiss law for solid and liquid compounds of the Gd–Al system. The Curie paramagnetic temperature p, the Curie–Weiss constant C, the temperature-independent susceptibility component, and the effective magnetic moments eff per REM atom are calculated on a computer by the least-squares method based on the dependence –1(T). The indirect exchange interaction parameter of the examined compounds is also calculated semi-empirically.  相似文献   

13.
Zusammenfassung Messungen des Imaginärteils der Suszeptibilität als Funktion der Mikrowellenfeldstärkeh wurden bei Hauptresonanz an Proben aus reinem und mit Dysprosium dotierten Yttrium-Eisen-Granat durchgeführt. Die Gestalt der (1/h)-Kurven urde auf Grund einer früher veröffentlichten Theorie behandelt. Der an der Probe 3 gemessene Verlauf von kann befriedigend mit Hilfe des Modells der unabhängigen Spinwellen interpretiert werden. Dasselbe gilt für die Messung an der Probe 2 mit Gleichfeld in [111]-Richtung. Die Steilheit der quasilinearen Kurvenabschnitte ist bei diesen(1/h)-Kurven von der GrößeH/H k abhängig. Die Spinwellenhalbwertsbreite wurde auf Grund des benützten Modells mit Hilfe des Maximums der Größeh bestimmt. Der an der Probe aus reinem YIG gemessene Verlauf von stimmt für den Fall des Gleichfeldes in [100]-Richtung mit dem Modell der stark gekoppelten Spinwellen gut überein. Die Messung an dieser Probe mit Gleichfeld in [111]-Richtung weist einen anderen Verlauf der (1/h) Kurve auf, welcher nicht durch den Einfluß der magnetokristallischen Anisotropie der YIG erklärt werden kann. Dies sollte eher der Anisotropie der GrößeH k zugeschrieben werden und wir vermuten, daß die letztgenannte Messung ein Verhalten widerspiegelt, das irgendwo zwischen den mit der Theorie diskutierten Extremfällen liegt. Dasselbe kann von der Messung an der Probe 2 mit Gleichfeld in [100]-Richtung gesagt werden.
Saturation effects at main resonance in YIG
The imaginary part of the susceptibility at main resonance was measured as a function of the microwave field intensityh on samples of pure YIG and also on YIG doped with Dy. The experimental results are compared with a theory published earlier. In particular the form of the(1/h) curves is discussed and also the way in which the spin wave relaxation frequencies can be determined.
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14.
The third-order non-linear susceptibility, (3)(; , , –), describing the phase conjugation by degenerate four-wave mixing (DFWM) is calculated for a three-level polar system under a two-photon resonance (TPR) condition. The part of the susceptibility expressed only by the transitional dipole moments and the part resulting from the permanent dipole moments are distinguished. The spectra of (3)(; , , –), as well as the DFWM power-reflection and power-transmission spectra near to the TPR, are modelled for polar molecules. The effect of enhanced reflectivity of TPR-DFWM is obtained numerically.  相似文献   

15.
Saturated absorption spectroscopy was applied to study the line shape of the molecular iodineX( = 0,J = 13,15) B( = 43,J = 12, 16) transition ( = 514.5 nm) in a transversal magnetic field as high as 0.51 T. The Zeeman structure of several hyperfine structure (hfs) components was completely resolved and a detailed study of the second-order Zeeman shift and splitting was made. The anisotropic Magnetic Susceptibility (MS) of the molecular iodine both in theB(43) (X = 7.3 ± 1 × 10–34 J/Oe2) and theX(0) [ = (0.6 ± 1) × 10–34 J/Oe2] states as well as the isotropic MS difference [0o = (2 ± 0.2) × 10–34 J/Oe2] was measured.  相似文献   

16.
The dispersion of the third-order electric susceptibilities(; , , –) and(; , 0, 0) of NaCl and KCl monocrystals has been calculated by means of experimental data on the electro-optic Kerr effect. The result has been obtained by using semi-classical models of anharmonic oscillators. An ionic contribution to the electro-optic coefficients has been presented. From the result obtained it follows that the third-order electric susceptibilities are of the order of 10–22 m2 V–2.  相似文献   

17.
Hwang  L.C.  Tsai  C.Y.  Tiao  C.J.  Wen  T.C. 《Optical and Quantum Electronics》2000,32(4-5):641-656
For the copper complex of pyrazinoporphyrazine AzaPhcCu(C(CH3)3)8 in CH2Cl2, we use nanosecond pulses to measure its third-order nonlinear optic effects at 532 nm. The results show that its effective third-order nonlinear refractive index n eff 2 (–7.85 × 10–10 esu) is larger than that of the AzaPhcCu(C12H25)4 and the CuPc(OC5H11)8. The reverse saturable absorption (RSA) of AzaPhcCu-(C(CH3)3)8 is demonstrated by the ratio of effective excited state to ground state absorption cross sections. The observed intersystem crossing lifetime isc of AzaPhcCu(C(CH3)3)8 (15 ns) and AzaPhcCu(C12H25)4 (45 ns) are longer than that of CuPc(OC5H11)8 (5.0 ns). The aza-substituents are suggested to form a S1(n, *) state as their lowest excited singlet-states, and their radiationless intersystem crossing rates (1/isc) are discussed with the spin-orbit coupling S|H SO|T and the vibronic coupling S|T effects between S1 and T1 states.  相似文献   

18.
A class of the asymptotically Euclidian space-times is shown to exist for which the Schwarzschild mass is equal to zero. The coordinate atlases of these space-times satisfy two additional conditions: k (-gg 0k )=0 and ik 0 0g ik - ik k 0g 0i =0. In aT-orthogonal metricgs 2=g 00 dt 2 -g dx dx these conditions take a simple form: 0(detg )=0 and (0 g )(0 g )=0.  相似文献   

19.
The tension of the interface between the equilibrium phases of a phase-separated polymer solution is obtained in the simplest mean-field approximation from the functional equation for the composition profile of the interface. For temperaturesT near the critical solution temperatureT c, i.e., for Flory parameter near c, and for high degrees of polymerizationN, the profile and tension scale with=N 1/2( c), just as do the compositions of the coexisting phases in mean-field approximation. The surface tension in the asymptotic limitN, c at fixedx, is found to be given bya 2/kT c (2c'/c)1/2 N -5/4(x), wherea is the lattice spacing of an underlying lattice (or, roughly, the length of a monomer),c andc are the vertical and total coordination numbers of the lattice, and(x) is a scaling function, known for allx, with the asymptotic behavior asx0 and asx. The latter implies that becomes independent ofN asN at fixedT nearT c; the former implies that becomes proportional toN –1/2(1–T/T c)3/2 asTT c at fixedN1, as found previously.  相似文献   

20.
An extended version of the noncollinear spin model bySawatzky et al. is developed to derive a dependence of the differential high field susceptibility on the degree of inversion of the ferrite MnFe2O4. Using the available data on the main molecular field coefficients it is shown that the present model imposes restrictions on values of. Determination of from the measurements of the field dependence of the saturated moments at low temperatures on samples with varying degrees of inversion reveals good quantitative agreement with the present model.  相似文献   

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