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1.
The microwave characteristics of Pb1?x Ca x Fe0.5Nb0.5O3 multiferroics (x = 0.0, 0.4, 0.45, 0.5, 0.55, 0.6), have been investigated as a function of frequency and substitution. The results depict ?13.99 dB reflection loss at 11.65 GHz in composition x = 0.6. Microwave absorption is enhanced with substitution of Ca2+ ions and undoped composition 0.0 behaves as electromagnetic shield. The model governing microwave absorption is discussed and different compositions for electromagnetic applications have been suggested. 相似文献
2.
V. G. Kravets A. N. Pogorelyi A. F. Kravets A. Ya. Vovk Yu. I. Dzhezherya 《Physics of the Solid State》2003,45(8):1530-1536
The reflectivity spectra and the magnetorefractive effect (MRE) of (Co50Fe50)x(Al2O3)1?x metal-dielectric granular films (0.07<x<0.52) are analyzed in the IR spectral range λ=2.5–25 µm. It is revealed that the specific features observed in the spectra at λ≈8.5 and 20 µm are associated with the excitation of phonon modes in the dielectric matrix. The magnetorefractive effect in the films is observed below the percolation thresh-old only in p-polarized light and above the percolation threshold for both the p and s polarizations. It is demonstrated that the optical properties of (Co50Fe50)x(Al2O3)1?x films in the IR spectral range, to a first approximation, can be interpreted in the framework of the effective-medium theory and the magnetorefractive effect can be explained in terms of the modified Hagen-Rubens relation. 相似文献
3.
R. S. Iskhakov S. V. Komogortsev E. A. Denisova Yu. E. Kalinin A. V. Sitnikov 《JETP Letters》2007,86(7):465-469
Magnetostructural methods are applied to determine the exchange bond percolation limit in (Co41Fe39B20)x(SiO2)1?x nanocomposites (x c = 0.30 ± 0.02), which separates the phase plane along the metal concentration axis into a superparamagnetic region and a ferromagnetic region. It is shown that, with respect to the singularities of the magnetization up to the magnetization saturation curves, the ferromagnetic region is further subdivided into three regions differing in the character of the spatial propagation of the magnetization ripples or in the magnetic correlation function characteristics. The fractal dimension of the nanocomposite magnetic microstructure near the percolation threshold is determined. 相似文献
4.
The optical activity of uniaxial γ1-(GaxIn1?x )2Se3 crystals (x=0.1, 0.2, 0.3, 0.4) is studied at T=295 and 77 K in the spectral range 0.5–0.8 πm. It is found that the cationic substitution In → Ga leads to a nonlinear increase in the specific rotation of the plane of polarization ρ and the component g 33 of the gyration tensor. It is shown that the gyrotropy of the crystals studied is determined by high-energy transitions whose energy exceeds the energy of the edge transitions and that the gyrotropy observed has a molecular origin. 相似文献
5.
N. V. Anshukova A. I. Golovashkin L. I. Ivanova I. B. Krynetskii A. P. Rusakov D. A. Shulyatev 《Physics of the Solid State》2005,47(9):1595-1599
For single-crystal samples of the (Sr1?xLax)3Ru2O7 ruthenates, the temperature dependence of the thermal expansion coefficient α(T)) is measured in the range 4.2–80 K. The effect of magnetic fields H ≤ 3.5 T on thermal expansion is analyzed. It is found that the (Sr1?xLax)3Ru2O7 ruthenates exhibit an anomalous (negative) thermal expansion coefficient in the temperature range T ≤ 18 K. The position and width of the anomaly revealed in the temperature dependence of the thermal expansion coefficient α(T)) depend substantially on the magnetic field. The origin of the thermal expansion anomaly in ruthenates, the correlation of this anomaly with the stability of the crystal lattice, and the common nature of the anomalies in the thermal properties of ruthenates and high-temperature superconductors are discussed. 相似文献
6.
M. M. Maior V. T. Vrabel I. P. Prits N. F. Korda M. I. Gurzan Yu. M. Vysochanskii 《Physics of the Solid State》2005,47(9):1734-1739
The dielectric properties of layered crystals of CuInP2(SexS1?x)6 solid solutions are studied at x = 0.02, 0.05, 0.20, and 0.40. At a low selenium content (x ≤ 0.05), the solid solutions undergo a transition to the phase with short-range polar order. This transition manifests itself as a diffuse maximum in the temperature dependence of the permittivity ε′(T). Ferroelectric ordering in the solid solutions under investigation is suppressed at x > 1. It is assumed that the structural disordering initiated by the substitution of atoms in the anion sublattice of the solid solutions at 0.1 < x < 0.75 leads to the formation of the state of structured glass. The dielectric relaxation dispersion observed in the radio-frequency range at temperatures of 80–140 K is associated with the freezing of the relaxation dynamics of individual copper atoms. 相似文献
7.
Magnetic ordering and spin reorientation in iron borates NdxGd1?xFe3(BO3)4 (x = 0.01, 0.04, 0.25, 1.0) are studied using a rare-earth spectroscopic probe. 相似文献
8.
The temperature dependences of the molar heat capacity at constant pressure, Cp, of Pb5(Ge1?xSix)3O11 crystals with x=0, 0.39, and 0.45 in the range 5–300 K, as well as of their permittivity, dielectric losses, and the pyroelectric effect, have been measured. Experimental data on the temperature behavior of the heat capacity are presented in the form of a sum of two Debye and one Einstein terms, Cp(T)=0.405CD1(ΘD1=160 K, T)+0.53CD2(ΘD2=750 K, T)+0.046CE(ΘE=47 K, T). Besides a peak in the region of the ferroelectric Curie point Tc=450 K for crystals with x=0, the temperature dependences of the heat capacity did not reveal any other pronounced anomalies. 相似文献
9.
The temperature and magnetic-field dependences of the magnetocaloric effect in manganites La1−x
Ag
x
MnO3 (x = 0.1; 0.15; 0.2) and La1−x
K
x
MnO3 (x = 0.1; 0.11; 0.13; 0.15; 0.175) were studied by a direct method. Large changes in the sample temperature were detected as
a magnetic field changed by ΔH = 10 kOe. Temperatures of the magnetocaloric effect maxima are near room temperatures. Field dependences of the magnetocaloric
effect show no signs of saturation in fields to 30 kOe. 相似文献
10.
The Raman spectra of Zn2 ? 2x CuxInxSe2 (ZCIS) semiconductor films designed for use as optically active layers in thin-film solar cells have been investigated. The Raman spectra of ZCIS films are characterized by the presence of the dominant mode A 1, which is observed in AIBIIIC 2 VI compounds with chalcopyrite structure. The spectra of CuInSe2 films (x = 1) obtained at low temperatures (T ≤ 400°C) contain and additional mode at 258 cm?1, which is due to the presence of the impurity CuxSe phase. All modes observed in the spectra of ZCIS films with a Zn concentration ≤20 at % obtained under optimal conditions (520–540°C) correspond to the symmetry of vibrations in the chalcopyrite structure. The broadening and blue shift of the A 1 mode occurring with an increase in the Zn concentration are indicative of degradation of the chalcopyrite crystal structure and the chalcopyrite → sphalerite phase transition at Zn concentrations exceeding 20 at %. 相似文献
11.
V. G. Yakovlev V. V. Mikhailin A. Yu. Romanenko O. M. Basovich E. G. Khaikina 《Moscow University Physics Bulletin》2009,64(5):519-522
The luminescent properties of AgLa1 − x
Eu
x
(MoO4)2 (x = 0.1, 0.2, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0) under laser excitation (λ = 337.1 nm) are studied. It is shown that, upon
substitution of Eu3+ for La3+, the symmetry of luminescence centers does not vary. According to the X-ray diffraction data, all samples have scheelite-like
structure; the pattern of variation in volumes of their unit cells counts in favor of the presence of a continuous series
of solid solutions. It is found that an increase in the europium concentration in AgLa1 − x
Eu
x
(MoO4)2 leads to an increase in the luminescence intensity with a maximum at x = 0.9. 相似文献
12.
V. G. Yakovlev V. V. Mikhailin A. Yu. Romanenko O. M. Basovich E. G. Khaikina 《Moscow University Physics Bulletin》2010,65(5):392-396
The luminescent properties of LiRbLa2 − x
Eu
x
(MoO4)4 (x = 0.002, 0.02, 0.1, 0.2, 0.5, 1.0, 1.5, 2.0) solid solutions are investigated under laser excitation {λex = 337.1 nm). It is established that the composition containing 50 at % Eu3+ is the brightest of the considered set of phosphors and has the highest quantum yield. 相似文献
13.
The phenomenological theory of phase transition in Pr0.6 Ca0.4 MnO3 manganite is developed. It is shown that this is the orbital phase transition and that the two electronic states of the manganese ion, which are discussed in the literature, result from two different types of condensation of the same orbital order parameter. Thus, the manganese ions in Pr1?xCax MnO3 manganites with 0.3≤x≤0.5 may be in either of the two electronic states, depending on the thermodynamic parameters. 相似文献
14.
The influence of Gd doping at La-site on the electrical transport properties and the colossal magnetoresistance of La0.7−x
Gd
x
Sr0.3MnO3 (x=0.00, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, 0.60, and 0.70) is studied. The experimental results indicate that the transport
properties exhibit abnormal behavior under high doping condition. Forx=0.50, we find that a transition from metal to insulator occurs after the occurrence of insulator-metal transition nearT
c, which seldom occurs in ABO3 structure. For samplesx=0.60 and 0.70, it exhibits insulator behavior far aboveT
c. These abnormal behaviors are attributed to different magnetic background, i.e. the system undergoes a transition from long
range ferromagnetic order to the cluster-spin glass state and further to antiferromagnetic order. 相似文献
15.
The effect of the photon energy of the exciting laser radiation on the Raman spectra of Ba1?xKxBiO3 with x=0.25, 0.40, and 0.50 is studied. An increase in the laser wavelength from 488 to 750 nm scarcely affects the amplitudes and frequencies of the spectral lines in the Raman spectra of the nonsuperconducting compound with x=0.25. For the optimally doped (x=0.40) and overdoped (x=0.50) superconducting compounds, a substantial increase in the line intensity and a considerable shift of the characteristic frequencies are observed. This result suggests that, in the whole range of superconducting compositions 0.37≤x≤0.50, the local symmetry of the Ba1?xKxBiO3 crystal lattice differs from the perfect cubic symmetry, which should take place according to the literature data. The fact that resonance phenomena are observed when the laser photon energy is shifted toward the optical gap testifies to the presence of local electron pairs in the whole range of superconducting compositions 0.37≤x≤0.50 and is evidence in favor of the superconductivity mechanism proposed for Ba1?xKxBiO3 on the basis of the X-ray absorption studies in our previous paper. 相似文献
16.
V. V. Mashkautsan R. I. Zainullina N. G. Bebenin V. V. Ustinov Ya. M. Mukovskii 《Physics of the Solid State》2003,45(3):494-498
A study of the temperature dependences of the ordinary and anomalous Hall coefficients and of the Hall mobility of carriers in single crystals of the ferromagnetic manganites La1?xSrxMnO3 (x=0.15, 0.20, 0.25) was carried out in the temperature interval from 85 to 400 K. The nature of the carriers and the conduction mechanisms in these compounds are discussed. 相似文献
17.
M. Markina T. Chistyakova N. Tristan B. Büchner A. Bush A. Vasiliev 《Journal of Experimental and Theoretical Physics》2007,105(1):18-20
Single crystals of Li x Na1 ? x Cu2O2 solid solutions have been grown from the melt and crystal lattice parameters have been studied. It is found that the solid solution of this system exists in the region x ≤ 0.25. Specific heat and magnetic susceptibility are investigated on monocrystalline samples with x = 0.07, 0.14, and 0.21. Long-range magnetic order in these compounds is formed at T = 13.8, 4.1, and 14.8 K, respectively. It is found that the Néel temperature T N in these compounds increases with Li content. 相似文献
18.
V. V. Ogloblichev A. V. Pogudin Yu. V. Piskunov S. V. Verkhovskii A. Yu. Yakubovsky A. Trokiner 《JETP Letters》2005,82(2):81-85
The Knight shift 207Ks for the 207Pb nuclei in the metal phase of the oxides BaPb1?xBixO3 (x < 0.35) has been analyzed as a function of the concentration. The shift, which is proportional to the density of states near the Fermi energy: 207Ks ~ N(EF), reaches a maximum for an oxide with the maximum superconducting transition temperature Tc(x ≈ 0.25) = 12 K. A significant increase in the width of the shift distribution with the Bi concentration testifies to the formation of a nonuniform state of the electronic system in the conduction band of superconducting oxides, which is accompanied by an increase in short-wavelength contributions to the spin susceptibility. To detect the 207Pb NMR spectra in superconducting oxides with x > 0.2, the 17O-207Pb spin-echo double-resonance method is used, which provides successful detection of the 207Pb NMR signal with an anomalously high rate of spin-spin relaxation T 2 ?1 > 500 ms?1. Thus, fundamental restrictions arising in investigations of rapidly relaxing 207Pb nuclei, which are “unobservable” in superconducting oxides BaPb1?xBixO3 when they are studied by traditional single-resonance methods of pulse NMR spectroscopy, have been overcome. 相似文献
19.
The isothermal changes in the magnetic entropy and the lattice entropy and the adiabatic temperature change in La(Fe0.88Si0.12)13 and La(Fe0.86Si0.14)13 ferromagnets in a magnetic field are calculated. The calculations are performed with a generalized magnetostriction model
of a ferromagnet; the calculation results are compared to experimental data. It is shown that the change in the lattice entropy
decreases the magnetocaloric effect and makes it possible to explain the experimental data obtained for La(Fe
x
Si1 − x
)13 (x = 0.86, 0.88) ferromagnets. The temperature dependences of the bulk compression moduli of these ferromagnets are calculated,
and these dependences indicate a strong lattice softening in the vicinity of the magnetic phase transition in them. The thermal
expansion coefficient and some magnetic properties of the ferromagnet with x = 0.86 are measured to determine the numerical values of the parameters entering into calculation formulas. 相似文献
20.
A. A. Bush K. E. Kamentsev R. F. Mamin 《Journal of Experimental and Theoretical Physics》2005,100(1):139-151
The special features of the dielectric properties and conduction of ferroelectric crystals of Pb5(Ge1?xSix)3O11 (0 ≤ x ≤ 0.67) solid solutions were studied. Permittivity anomalies close to the temperatures T1 ≈ 260 K and T2 ≈ 130 K, the appearance of relaxator behavior at x > 0.35, and critical behavior of the concentration dependences of dielectric and pyroelectric characteristics at x1 = 0.35 and x2 = 0.60 were observed and studied. These phenomena were found to be related to the dynamics of charge localization on defects with activation energies of Ua1 ≈ 0.6 eV and Ua2 ≈ 0.23 eV. Relaxator behavior appears when the Curie point lies in the temperature region of thermal charge localization. The concentration dependence features at x1 and x2 are explained by the coincidence of the Curie point and the centers of the temperature regions of charge localization on the Ua1 and Ua2 defect levels, respectively. 相似文献