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1.
J. Maetz M. Müllner H. Jex W. Assmus R. Takke 《Zeitschrift für Physik B Condensed Matter》1980,37(1):39-45
The structures of LaAg
x
In1–x
alloys withx=0.75, 0.89 are determined by neutron diffraction on powder samples. The space group isI4/mmm (D
4h
/17
). The lattice constants splitting, the order parameter and the mean square vibrational amplitudes of the atoms are given in the temperature range from 20 KT300 K. 相似文献
2.
M. A. Jafarov E. F. Nasirov S. A. Mamedova R. F. Mekhtiev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2014,8(1):131-137
Various negatron effects in films of alloys of II–VI compounds deposited from solutions as a function of the deposition mode and heat treatment are studied. It is found that the negative photocapacitance effect, which was first discovered in ZnS1?x Se x films, and the slowly relaxing negative photoelectric effects, which are caused by the transition of electrons located in a nanoscale surface layer from the shallow energy levels of trapping centers to deeper levels with a lower polarizability and by the presence of nanoscale clusters in these materials, which play the role of a “reservoir” for minority charge carriers, occur according to a single mechanism. A model to explain the basic laws of negative photoconductivity in CdSe1 ? x Te x films deposited from a solution is proposed. Negative residual conductivity is explained in terms of double-barrier relief model, while negative differential photoconductivity is attributed to the presence of nanoscale electric domains. 相似文献
3.
4.
Different chemical and/or geometrical orders were found in melt-spun DyMn6???x Ge6???x Fe x Al x with x = 2.5 and 3 having fully amorphous and mixed (crystalline and amorphous) structure, respectively. Thermal variations in magnetization M from liquid helium up to room temperature for both samples are similar. Magnetization value at zero field cooled curve reaches about 0.1 μB per formula unit at 2 K and then increases. Two maxima are visible, the first at 50 K (a sharp effect) and the second very broad ranging from 150 to 200 K. 57Fe Mössbauer spectrometry investigation revealed a remaining magnetic component in addition to a prevailing quadrupolar feature. Application of a weak external magnetic field causes an increase in the mean hyperfine magnetic field B hyp and the volume fraction of magnetic component. This observation was confirmed by results of M(T), M(H) and AC magnetic susceptibility measurements. In short-range ordered crystallographic zones characteristic of melt-spun DyMn6???x Ge6???x Fe x Al x (x = 2.5, 3) alloys, the related magnetic ordering, called the mictomagnetism or the cluster spin glass appears. 相似文献
5.
The paper reports on surface morphology, structure and microhardness of TiSi–N films formed by cosputtering from two target-facing unbalanced magnetrons, equipped with pure Ti and Si targets, on an unheated substrate rotating in front of both targets. The ratio Si/Ti in the TiSi–N film was achieved by modifying the magnitude of currents in the individual magnetrons and by the addition of nitrogen to the film. The rotation of the substrate has a strong effect on the film deposition rate and its morphology. The deposition rate is 3 times lower than that of the film deposited on a stationary substrate. The surface roughness of a polycrystalline Ti film deposited on the rotating substrate is considerably higher than that on a stationary substrate. On the contrary, the surface of an amorphous Si film is smooth and there is no difference between the roughness of Si films sputtered on stationary and on rotating substrates. The hardness of the film increases with increasing Si content and with the addition of nitrogen to the TiSi film. The Ti(26 at.%)Si(8.5 at.%)N(65 at.%)-film sputtered on an unheated rotating steel substrate, held at a floating potential, exhibited the best result with a hardness of 29 GPa. 相似文献
6.
The crystallization behaviour of about 60 samples of electrodeposited Fe1–x
P
x
, 0.09<x<0.26, was investigated with DSC and X-ray diffraction. Several subsequenting transformations during heating at 10 K/min were identified. The corresponding transformation temperatures, reaction heats and reaction rates were measured. If the as-deposited samples contain metal-rich crystallites (microcrystalline and partly amorphous material) crystallization starts with primary precipitation of -iron followed by polymorphous crystallization of Fe3P. In amorphous samples these two processes become less important compared with the eutectoid reaction the higher the phosphorus content. In a small concentration range around 19 at% P this transformation is the only one. Above this range the primary crystallization of Fe3P becomes more and more dominant. 相似文献
7.
8.
V. V. Rylkov S. N. Nikolaev K. Yu. Chernoglazov B. A. Aronzon K. I. Maslakov V. V. Tugushev E. T. Kulatov I. A. Likhachev E. M. Pashaev A. S. Semisalova N. S. Perov A. B. Granovskii E. A. Gan’shina O. A. Novodvorskii O. D. Khramova E. V. Khaidukov V. Ya. Panchenko 《JETP Letters》2012,96(4):255-262
It has been found that the Curie temperature (T C ?? 300 K) in nonstoichiometric Si1 ? x Mn x alloys slightly enriched in Mn (x ?? 0.52?C0.55) in comparison to the stoichiometric manganese monosilicide MnSi becomes about an order of magnitude higher than that in MnSi (T C ?? 30 K). Deviations from stoichiometry lead to a drastic decrease in the density of charge carries (holes), whereas their mobility at about 100 K becomes an order of magnitude higher than the value characteristic of MnSi. The high-temperature ferromagnetism is ascribed to the formation of defects with the localized magnetic moments and by their indirect exchange interaction mediated by the paramagnetic fluctuations of the hole spin density. The existence of defects with the localized magnetic moments in Si1 ? x Mn x alloys with x ?? 0.52?C0.55 is supported by the results of numerical calculations performed within the framework of the local-density-functional approximation. The increase in the hole mobility in the nonstoichiometric material is attributed to the decay of the Kondo (or spin-polaron) resonances presumably existing in MnSi. 相似文献
9.
In this paper, we report on measurements of the specific heatC of single-crystalline Eu
x
Sr1–x
Te at temperatures between 60 mK and 15 K and in magnetic fields up to 6 T. Pure antiferromagnetic EuTe shows unusual critical behavior in the vicinity of the Néel temperatureT
N=9.8 K with a positive critical exponent instead of the 3d-Heisenberg exponent =–0.12. Possible reasons for this discrepancy between theory and experiment include magnetic anisotropy effects due to magnetic dipole-dipole interactions, which may give rise to a cross-over of the critical behavior very close toT
N. This anisotropy is also seen in the specific heat below 1 K where an exponential decay ofC is observed, and in the dependence of the magnetic susceptibility on the direction of the applied field. With increasing dilution of EuTe with nonmagnetic Sr, the critical behavior changes: becomes negative and decreases continuously towards –1 atxx
c. This concentration dependence of was previously observed in the diluted ferromagnetic system Eu
x
Sr1–x
S. Our data thus support that the apparent change in the critical behavior depends on the degree of disorder. Samples with concentrationx lower than the critical concentrationx
c reveal spin-glass behavior in the specific heat. In addition, the dependence ofT
N on magnetic fields is discussed. The data yield a normalized magnetic phase boundaryB
c(T)/Bc(T=0) vs.T
N(B)/TN(B=0) which is independent of concentration. 相似文献
10.
, Bi2Te3–x
Se
x
. , , . , , . .
Influence of oxygen content on electric and thermoelectric properties of ternary system Bi2Te3–x Se x
A study is made of the influence of oxygen, contained in the semi-conducting system Bi2Te3–x Sé x , on the electric and thermoelectric properties. It is shown that the addition of oxygen to the prepared samples Bi2Te2.4Se0.6 causes a decrease in electric conductivity while the thermoelectric force remains unchanged. This influence is connected with a decrease in the mobility of the electrons but their concentration is not influenced by the presence of oxygen. Conclusions are reached as to the influence of oxygen on the efficiency of the conversion of thermal energy into electric energy and vice versa.相似文献
11.
12.
The structural and electrophysical characteristics of a series of solid solutions of layered perovs-kite-like oxides Bi6 ? x Sr x Ti2 ? x Nb2 + x O18 (x = 0, 0.25, 0.5, 1.0, 1.5, 2.0) have been studied. The temperature dependences of the relative permittivity ?/?0(T) and dielectric loss tangent tanδ have been measured. The dependences of the maximum of the permittivity ?/?0, Curie temperature T C, lattice parameters, and the unit cell volume on x have been obtained. The structural parameter a, which corresponds to the polar direction, and the value of the orthorhombic distortion of the unit cell have been found to demonstrate noticeable negative deviations from the Vegard’s law. It has been established that the variations of the orthorhombic distortion correlate with the variations of the permittivity maximum; however, they do not markedly influence the Curie temperature that varies linearly over entire range of changes in x. 相似文献
13.
A diluted antiferromagnet Fe
x
Mg1–x
TiO3 has been shown to behave as a spin glass (x=0.2) and a reentrant spin glass (x=0.3) near the Fe percolation concentrationx 0.25. In order to obtain microscopic information on these samples, we performed Mössbauer measurements. At considerably higher temperatures than the transition temperatures, magnetically broadened spectra appear superimposed upon the paramagnetic doublets. A remarkable feature is that the intensity of the magnetic spectra increases accompanying the decrease of their linewidth. This behavior can be ascribed to the gradual slow-down of fluctuations of the antiferromagnetic clusters formed at high temperatures. To investigate the temperature variations of the relaxation time of the clusters, we analyzed the Mössbauer spectra using the method formulated by Blume. It has been shown that becomes long with decreasing temperature and the rate of the slow-down of is hastened aroundT
SG andT
N. 相似文献
14.
R. S. Iskhakov L. A. Chekanova I. G. Vazhenina 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(10):1265-1267
Gradient films of ferromagnetic 3d metals with prescribed magnetic potential profile along the film thickness are obtained. It is found that the spin-wave resonance spectrum in these films is characterized by anomalous dependences of resonance fields of spin-wave modes H r on the mode number: H r(n) ~ n, H r(n) ~ n 2/3. 相似文献
15.
ZF, LF and TF SR experiments with antiferromagnetic (AF) ceramical samples La2–x
Sr
x
CuO4–y
have been performed in the temperature range 10–300 K. Zero field muon spin polarization functions obtained below the Neel temperature clearly show a nonzero initial precession phase-–0.35 rad. We propose an explanation based on existence of the dynamical magnetic fields on the muon.We thank Drs. A.G. Chistov and A.M. Brjazkalo from RSC Kurchatov Institute for the preparation the #2 La2CuO4–y
sample. 相似文献
16.
Based on the assumption of a high-moment-low-moment instability of the Mn atom, we construct a simple spin model with coupled magnetic and spatial degrees of freedom to describe the Laves phase systems Y(Mn x Al 1 m x ) 2 and Y x Sc 1 m x Mn 2 . Monte Carlo simulations of this model qualitatively reproduce anomalies observed in these materials like a discontinuous giant volume change and anomalous thermal expansion behavior. 相似文献
17.
Lei Zhang Jiyu Fan Xiangde Zhu Wei Ning Zhe Qu Min Ge Li Pi Yuheng Zhang 《Applied Physics A: Materials Science & Processing》2013,113(1):201-206
The doping of bromine has prominent effect on the transport properties of CuCr2Se4, where the conductivity of CuCr2Se4?x Br x changes from metallic behavior with x=0 to semiconductor with x=1. In this work, the critical behavior of single crystal CuCr2Se4?x Br x with x=0.25, which lies at the boundary between the metallic and insulating state, is investigated through the magnetization under high magnetic field. The critical exponents β=0.39±0.03 and γ=1.25±0.05 are obtained by the Kouvel–Fisher method, and δ=4.79±0.01 is generated by the critical iso-thermal analysis. The obtained exponent β is close to the prediction of the three-dimensional (3D) Heisenberg model, while γ approaches that of the 3D-Ising model. Although the bromine doping has prominent effect on the transport behavior, the critical exponents are hardly changed. The obtained results indicate that the ferromagnetism is established through one-dimensional Cr–Se–Cr bonds. However, the nearest-neighbor magnetic interaction belonging to the 3D-Heisenberg model also contributes to the ferromagnetic exchange. 相似文献
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19.
E. A. Vinogradov B. N. Mavrin N. N. Novikova V. A. Yakovlev D. M. Popova 《Laser Physics》2009,19(2):162-170
Recently ultrabroadband infrared solid state lasers based on a new vibronic material Cr2+:ZnSe x S1–x were demonstrated [1–3]. Cr2+ ion substitutes the metal ion (tetrahedral sites), the crystal field of the solid solution is responsible for large inhomogeneous broadening of Cr2+ electron states. The crystal field can be reconstructed by investigation of lattice dynamics — optical phonon parameters and dielectric function in IR. We paid special attention to investigation of vibrational and infrared spectroscopic properties of ZnSe x S1 ? x crystals. A very interesting and somewhat unexpected result of these studies was the existence in the crystals of effective S-Se dipoles, which generate an additional deep dynamically charged level in the forbidden gap of the semiconductors. The results of the first-principles calculations of both the phonon structure and the electron localization in ZnSe x S1–x crystals as well as acceptor levels in Cr2+: ZnSe crystal are discussed. 相似文献
20.
在曝光过程中如果降低x射线的能量,可揭示隐藏的缺陷。降低电压的x射线摄影术已被用来探测薄金属片中的裂缝,该金属片由两倍于其厚度的未破裂薄片复盖。最初研制它是为了检验多层电路板上的焊接,该技术有可能用于其它无损检验。 相似文献