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1.
Eu(Ir1–x Pd x )2Si2 solid solutions which exist only for 0x0.125 and 0.75x1 crystallize in the tetragonal ThCr2Si2-type structure. X-ray diffraction data, magnetic susceptibility and151Eu Mössbauer measurements suggest that these compounds can be characterized as homogeneous mixed valence systems. At room temperature and for 0x0.125, the europium valence decreases asx increases. For 0.75x1, a sharp continuous valence transition from Eu2+ to Eu3+ occurs near 48 K, 54 K and 78 K forx=0.75, 0.81 and 0.94 respectively. These valence changes are discussed in relation with the Eu–(Ir, Pd) interatomic distance.  相似文献   

2.
Powder samples of ErBa2Cu3Ox prepared by a desorption-absorption procedure were studied by susceptibility and neutron-diffraction experiments for variousx(6x7). The suppression of superconductivity does not coincide with the orthorhombic-to-tetragonal phase transition, but with a significant charge redistribution between the Cu–O chains and planes. Upon oxygen removal, asT c (x)O, step-like anomalies are observed in some bonding lengths and atomic distances, which support an all-electronic mechanism for the oxide superconductivity.  相似文献   

3.
We report the results of measurements on metallic glasses of the form Y66(Fe1–x M x )34. For M = B we find that there is an extended range of glass formation (0x0.40) and that properties such as atomic density, electrical resistivity, microhardness, and thermal stability are functions ofx. For M = C, Si, or Ge we find a restricted range of glass formation (0 x0.10) and no significant changes in the properties of the glasses. Using Fe57 Mössbauer effect spectroscopy we find that the M = B case is again unique in that the structure of the glass is sensitive to B content. We relate the differences in glass formation for the M = B and M = C, Si, Ge glasses to the existence of Y rich compounds in the C, Si, and Ge cases and the lack of such compounds in the M = B case.  相似文献   

4.
Single-phase non-stoichiometric Ba2YCu3O6.5+x with –0.248x0.300 can be obtained by annealing prereacted samples at 0.01–1 bar oxygen partial pressure. Samples withx=–0.248 are semiconducting, samples at 0.239x0.300 are metallic withT c increasing from 92.2 to 94.0 K for annealing in 0.02–1 bar O2.  相似文献   

5.
The phase composition of the mixed oxides, series LiMe x V2–x O4, where Me=Zn, Mg, was studied using X-ray analysis. The minor phases present in the investigated samples together with the basic spinel phase were determined as Li3VO4 and Zn2V2O7 or Mg2V2O7 respectively. Their presence is caused by the tendency of tetravalent vanadium ions to the disproportionation. For the compositionsx=0·375 were determined the quantitative phase compositions. The lattice constant of the spinel phase is linearly changing according to Vegard's rule, for the zinc series in the range 0x0·375 and for the magnesium series in the range 0xs0·25. Further substitution in magnesium series caused tetragonal deformation of the cubic spinel lattice.The author is indebted to Dr. A.Bergstein for helpful discussions and to Mrs. E.Hrubá for technical assistance.  相似文献   

6.
If (, ,P, ) is an event-state-operation structure, then the events form an orthomodular ortholattice (, , ) and the operations, mappings from the set of states into , form a Baer *-semigroup (S, , *, ). Additional axioms are adopted which yield the existence of a homomorphism from (S, , *, ) into the Baer *-semigroup (S(), , *, ) of residuated mappings of (, , ) such thatx S maps states while x S () maps supports of states. If (, , ) is atomic and there exists a correspondence between atoms and pure states, then the existence of provides the result: (, , ) is semimodular if and only if every operationx S is a pure operation (maps pure states into pure states).Supported in part by the United States Atomic Energy Commission and in part by the Fonds National Suisse.  相似文献   

7.
The specific electrical resistivityp(T) was measured for the reentrant spin glass system (Fe0.65Ni0.35)1–x Mn x (0x0.102) in the temperature range 4 KT280 K. We used our own phenomenological ansatz to explain the results obtained in order to provide the fitted parameters with physical meaning. The cause of the observed minimum in the measured curves can be given by a model of local magnetism.  相似文献   

8.
This paper presents an extensive study on the dependence of the mean number of the fast fragment of the target nucleus n g on the incident beam energy in proton-nucleus interaction in emulsion in the range 6·2E 0400 GeV/c. It has been observed that n g decreases in the range 6·2E 0200 GeV/c, then increases and attains an approximately steady value up to 400 GeV/c. It is very difficult to explain this behaviour with the help of the existing nuclear production models.The author would like to thank Prof A. J. Herz (CERN), Prof. K. D. Tolostov (Dubna, U.S.S.R.), Prof. P. L. Jain (State University of New York, U.S.A.), Prof. G. Giacomelly (Italy) for kindly supplying the exposed emulsion plates.  相似文献   

9.
Refractive-index and optical-absorption spectra of Bi-substituted yttrium iron garnet films, epitaxially grown by liquid-phase epitaxy, have been measured in the spectral regime 0.26 m1.9 m by thin-film interference for 0.52 m and by ellipsometry for0.52 m. The Y3–x–y Bi x Pb y Fe5–z Pt z O12 films contain bismuth in the range Ox 1.42, lead in the range 0.01 y0.08 and platinum in the range 0.005<=z0.03. There is satisfactory coincidence between the results from ellipsometry and thin-film interference in the overlapping wavelength region. The materials investigated are the same as reported earlier from this laboratory in ter mof their magnetic and magnetooptic properties.  相似文献   

10.
A mathematical procedure which gives an opportunity to distinguish between relaxation and distribution mechanisms of the Mössbauer line broadening is proposed. It is based on the method of Mössbauer line sharpening developed recently [1] and allows one to answer unambiguously the question whether or not relaxation manifests itself in Mössbauer measurements by examining the wings of the spectrum. The procedure is applied to the spectra of high spin ferric metmyoglobin and (Fe0.65Ni0.35)1–x Mn x alloys. Analysis of the metmyoglobin spectra manifests the presence of the relaxation influence in the temperature range 10 KT100 K. Analysis of the alloy spectra shows that for the temperatures 4 KT300 K and Mn concentrations 0x0.245 no relaxation is observed and the line broadening is mainly caused by the distributions of magnetic hyperfine fields. A possible explanation of this result is given.  相似文献   

11.
The total dynamic structure factorsS(Q, ) of icosahedral, glassy Pd58.8Si20.6U20.6, and the crystallized sample have been determined at room temperature using inelastic scattering of cold neutrons (IN6 of ILL). In contrast to the static structure factorS(Q), where the long range bond orientational order (BOO) leads to pronounced diffraction peaks with finite half width, the dynamic structure factor shows little or no influence of the long range BOO on the atomic dynamics of icosahedral PdSiU in the range of frequencies (0.525 meV) and momentum transfers Q(5Q30 nm–1 for inelastic scattering) investigated here. The wavelength-dependence of the atomic dynamics of icosahedral PdSiU is very similar to that of the metallic glass and is different from that of the crystallized sample. As for glassy PdSiU no well defined vibrational collective excitations are found as peaks in the inelastic part ofS(Q, ) of the icosahedral sample,-quite in contrast to theoretical expectations and to the dispersions of pronounced excitations determined under identical experimental conditions fromS(Q, ) of the crystallized sample. On structural relaxation of the metallic glass Pd58.8Si20.6U20.6 the largest amount of low energy modes is annealed out at lowest energy.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday  相似文献   

12.
The specific heat in (KBr)1–x(KCN)x has been measured for concentrations 0.00x0.93 and for temperatures 2 KT50 K. In addition, the dipolar relaxation phenomena were studied using dielectric spectroscopy. The relaxation behaviour was parametrized assuming a Gaussian distribution of energy barriers and the mean activation energies, the distribution widths, and the attempt frequencies have been determined as a function of the CN concentration. With these parameters the linear and the excess specific heat contributions were calculated and compared to the calorimetric results.  相似文献   

13.
The isothermal magnetic susceptibility (x) of the completely miscible liquid Pd1–x Si x alloy system shows a rapid monotonous decrease withx from strong paramagnetism to weaklyx-dependent diamagnetism. The measured susceptibility isotherm at 1825 K is analysed within 0x1 by using a semiphenomenological method of decomposing the magnetic susceptibility into its constituent parts. Because of the empirical similarity between liquid and glassy metals this interpretation also provides assertions about the magnetism of glassy Pd1–x Si x aroundx=0.2.  相似文献   

14.
In the relativistic quantum field theory the representation for theS-matrix elements is obtained for any coupling constantsg in the case of a one component scalar field (x) with nonlocal nonpolynomial interaction I ()=gU() when the causal function is bounded in the Euclidean region 0D c (x E 2 D c (0)< and the function |U(u)|1 for realu. It is proved that the two point Green function is bounded in the physical region of momenta variablep 2.  相似文献   

15.
The measurements of the proton (NMR) spinlattice relaxation times have been made in a series of ytterbium hydrides, YbH x . Results are reported forx=1.80, 1.95, 2.00 and 2.62 and temperatures 4.2T297K. In the orthorhombic phase (1.80x2.00), the spin-lattice relaxation times are dominated by the hyperfine interaction of protons with conduction electrons and the spin diffusion mechanism. In the cubic phase (x=2.62), the relaxation times are five orders of magnitude shorter than in the orthorhombic one. This is interpreted in terms of the proton coupling with the Yb3+ ion spin fluctuations.  相似文献   

16.
The Gd ESR and magnetic susceptibility of Y1–xCexAl2 (0.01x1) were measured in the temperature range 1.5–25 K (ESR) and 2.6–290 K (), respectively. The Gd ESR spectrum is substantially altered in the presence of Ce ions. The Gd resonance linewidth shows a non-linear temperature dependence which is more pronounced for higher Ce concentrations. A model is suggested to explain the linewidth behaviour and to estimate the spin fluctuation time of Ce ions in this system.  相似文献   

17.
The anisotropy constants K1 for systems MnxFe3–xO4, with 1x 1·8, are calculated on the basis of the one-ion model and it is shown that the anomalous temperature dependence of the constant K1 can be explained by the presence of Mn3+ ions in octahedral positions. The influence of the spin order on the magnetic anisotropy and the uniaxial anisotropy in systems MnxFe3–xO4 are discussed.  相似文献   

18.
The weak variation of the magnetic bulk susceptibility of Pd1–x Ag x with temperature T and silver mole fractionx within 0.5x1 has been investigated in the range 5KT400K. Experimental evidence can be given for an intersection point of the susceptibility isotherms (T=const,x) atx=0.55. The observed dependence of on T andx is interpreted by means of a semiphenomenological alloy susceptibility function (T,x).  相似文献   

19.
Neutron diffraction, neutron spectroscopy and magnetization measurements have been employed to study the structural, electronic, and magnetic behavior of eleven compounds with the general formula Nd1+y Ca v Ba2–y–v Cu3O x (0y0.5; 0v0.25; 6x7). The structure turned out to react to oxygen reduction similar as other 123-compounds, yielding discontinuities close to the metal-insulator-transition and the well-known relations of bond lengths as a function ofT c. The crystalline electric field (CEF) interaction, splitting the 10-fold degenerate ground-state J-multiplet of the Nd3+-ions into five doublet states, was investigated by neutron spectroscopy. The derived CEF parameters have been used to determine changes in the electronic surroundings of the Nd3+ ions. In addition, with the help of the CEF parameters the thermodynamic magnetic properties of these compounds were calculated which turn out to be in good agreement with the experimental data.  相似文献   

20.
LetH p =–1/2+V denote a Schrödinger operator, acting inL p v , 1p. We show that (H p )=(H 2) for allp[1, ], for rather general potentialsV.  相似文献   

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