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1.
CrxGe1–x (x 0.08) films were grown on GaAs (001) and Ge (001) substrates using molecular beam epitaxy (MBE) method, and their magnetic and transport properties have been studied in the temperature range between 1.8 and 300 K. All of the films exhibited weak paramagnetic behavior. Transport measurements showed that magnetoresistance ratio and the anomalous Hall resistance depend on the Cr concentration x and the kinds of substrate. 相似文献
2.
Guoqiang Qin Dongchun Li Zhouwen Chen Yinglan Hou Zhijun Feng Shimin Liu 《Computational Materials Science》2009,46(2):418-424
The goal of this paper is to undertake a detailed first principle calculation of the structural, electronic and optical properties of Sn1−xSbxO2. The results show that the stability of Sn1−xSbxO2 in the full range of Sb content points to the probability of a continuous solid solution, where the increasing Sb content leads to volume expansion with different variation trends in the lattice constants. The increase of Sb concentration in the semiconductor–metal–semimetal transition occurs in consonance with the corresponding changes in its structural, electronic and optical properties. Two competing mechanisms play essential roles in this transition, namely; the many body effect and the atom disorder. Our calculations concur with previous X-ray diffraction, sheet resistance, resistivity and optical parameters detections. The studies present a practical way of tailoring the physical behaviors of Sn1−xSbxO2 through the alloying technique. 相似文献
3.
I. A. Chaban 《Journal of Superconductivity》1993,6(6):351-358
The impurity mechanism proposed earlier is used to interpret the transport properties of high-temperature superconductors in the normal state. Temperature and impurity concentration dependences of the resistance and the Seebeck and Hall coefficients are discussed. An explanation for the sharp drop in the Seebeck and Hall coefficients with impurity concentration and reducing them to zero in La2–x
Sr
x
CuO4 at the maximumx at which superconductivity exists is put foward. 相似文献
4.
AbstractThe superconducting transition temperature, Tc, in iron-based solids can be enhanced by applied pressure: Tc increases from 8 to 37 K for the 11-type FeSe when the pressure is raised from 0 to 4 GPa. High-pressure studies can elucidate the mechanism of superconductivity in such novel materials. In this paper, we present a high-pressure study of Fe(Se1?xTex) and Fe(Se1?xSx). In the case of Fe(Se1?xTex), the maximum Tc under high pressure did not exceed the Tc of FeSe, which can be attributed to the structural transition to the monoclinic phase. For Fe(Se1?xSx) (0 < x < 0.3), Tc exhibited a significant increase with pressure; however, the maximum Tc under high pressure did not exceed the Tc of FeSe. This may be due to the disorder induced by substituting S for Se, which is similar to the pressure effect on Tc for the 1111-type superconductor Ca(Fe1?xCox)AsF. The Tc of Fe(Se1?xSx) showed a complex behavior below 1 GPa, first decreasing and then increasing with increasing pressure. From high-pressure x-ray diffraction measurements, the Tc (P) curve was correlated with the local structural parameter. 相似文献
5.
Skutterudite compounds Co4Sb12-xTex (0.1 ≤ ×≤0.8) was synthesized successfully by high temperature and high pressure (HTHP) method and characterized with X-ray diffractometry and thermoelectric properties measurements. The samples prepared by HTHP are nearly with the single phase CoSb3. The electrical resistivity, Seebeck coefficient and thermal conductivity were all depending on synthetic pressure and the Te content of the Skutterudite compounds were performed at room temperature. As our expected, the Seebeck coefficient increased with an increase of the synthetic pressure and the thermal conductivity decreased with an increase of the synthetic pressure. These results indicated that HTHP technique may be helpful to prepare thermoelectric materials with enhanced thermoelectric properties. 相似文献
6.
A series of zirconium sulphoselenide (ZrS
x
Se3−x
, where x = 0, 0·5, 1, 1·5, 2, 2·5, 3) single crystals have been grown by chemical vapour transport technique using iodine as a transporting
agent. The optimum condition for the growth of these crystals is given. The stoichiometry of the grown crystals were confirmed
on the basis of energy dispersive analysis by X-ray (EDAX) and the structural characterization was accomplished by X-ray diffraction
(XRD) studies. The crystals are found to possess monoclinic structure. The lattice parameters, volume, particle size and X-ray
density have been carried out for these crystals. The effect of sulphur proportion on the lattice parameter, unit cell volume
and X-ray density in the series of ZrS
x
Se3−x
single crystals have been studied and found to decrease in all these parameters with rise in sulphur proportion. The grown
crystals were examined under optical zoom microscope for their surface topography study. Hall effect measurements were carried
out on grown crystals at room temperature. The negative value of Hall coefficient implies that these crystals are n-type in nature. The conductivity is found to decrease with increase of sulphur content in the ZrS
x
Se3−x
series. The electrical resistivity parallel to c-axis as well as perpendicular to c-axis have been carried out in the temperature range 303–423 K. The results obtained are discussed in detail. 相似文献
7.
A. Szasz J. Hajdu J. Kojnok Z. Dankhazi W. Krasser T. Trager J. Bankuti 《Journal of Superconductivity》1990,3(4):425-431
A definite correlation between the thermal and electronic properties of Y1Ba2Cu
x
O
y
perovskite materials has been observed using differential thermal analysis (DTA) and X-ray fluorescence spectroscopy (XFS). The compound Y1Ba2Cu3O7–z
shows anomalous transition enthalpy and copper-oxygen hybridization with respect to other compounds with different copper content. 相似文献
8.
9.
AbstractWe have characterized the electronic structure of FeSe1?xTex for various x values using soft x-ray photoemission spectroscopy (SXPES), high-resolution photoemission spectroscopy (HRPES) and inverse photoemission spectroscopy (IPES). The SXPES valence band spectral shape shows that the 2 eV feature in FeSe, which was ascribed to the lower Hubbard band in previous theoretical studies, becomes less prominent with increasing x. HRPES exhibits systematic x dependence of the structure near the Fermi level (EF): its splitting near EF and filling of the pseudogap in FeSe. IPES shows two features, near EF and approximately 6 eV above EF; the former may be related to the Fe 3d states hybridized with chalcogenide p states, while the latter may consist of plane-wave-like and Se d components. In the incident electron energy dependence of IPES, the density of states near EF for FeSe and FeTe has the Fano lineshape characteristic of resonant behavior. These compounds exhibit different resonance profiles, which may reflect the differences in their electronic structures. By combining the PES and IPES data the on-site Coulomb energy was estimated at 3.5 eV for FeSe. 相似文献
10.
T. Sun Y. G. Zhao R. Fan X. P. Zhang B. G. Liu Y. H. Xiong P. J. Li 《Journal of Superconductivity》2004,17(3):473-480
AlB2 and MgB2 are neighboring compounds and have similar crystal structures. However, their superconducting properties are very different because the holes which play a key role in the superconductivity of MgB2 do not exist in AlB2. In this paper we reported our attempts to dope holes into AlB2 by substituting Li and vacancy for Al, and these holes were expected to induce superconductivity in the system. However, experimental results showed that Li was hard to substitute Al in AlB2. The variation of resistivity with temperature and x for samples with the nominal composition of Al1–xLi
x
B2 was analyzed by considering the phase variation of the samples with x. The temperature dependence of resistivity for Al1–xB2 was also studied and orders of magnitude change in resistivity was observed when x was up to 0.4 and 0.5, similar to that observed in Mg1–xB2 system by Sharma et al. (A. Sharma, N. Hur, Y. Horibe, C. H. Chen, B. G. Kim, S. Guha, Marta Z. Cieplak, and S. W. Cheong, Phys. Rev. Lett.
89, 167003 (2002)). It is proposed that phase separation may exist in Al1–xB2, leading to the dramatic change of resistivity because of percolation. 相似文献
11.
S S Shinde K M Jadhav G K Bichile Bimal S Trivedi R G Kulkarni 《Bulletin of Materials Science》1998,21(5):409-413
The structural and magnetic properties of the mixed spinel Co1+x Si x Fe2?2x O4 system for 0·1≤x≤0·6 have been studied by means of X-ray diffraction, magnetization, and Mössbauer spectroscopy measurements. X-ray intensity calculations indicate that Si4+ ions occupy only tetrahedral (A) sites replacing Fe3+ ions, and the added Co2+ ions substitute for (B) site Fe3+ ions. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe3+ at the A and B sites, forx≤0·3. The Mössbauer intensity data shows that Si possesses a preference for the A site of the spinel. The variation of the saturation magnetic moment per formula unit measured at 300 K with the Si content, is explained on the basis of Neel’s collinear spin ordering model forx≤0·3 which is supported by Mössbauer, and X-ray data. The Curie temperature decreases nearly linearly with increase of the Si content, forx=0·1–0·6. 相似文献
12.
13.
The layer type MoSe
x
Te2−x
(0 ≤x ≤ 2) have been grown in single crystalline form by chemical vapour transport technique using bromine as the transporting
agent. The electrical resistivity and Hall mobility perpendicular to thec-axis of the crystals were measured at room temperature. The variation of the Seeback coefficient with temperature was also
investigated. 相似文献
14.
We have investigated the effect of Sb/Ga flux ratio on the magnetic and electronic properties of Mn-incorporated GaSb random and digital alloys grown by low-temperature molecular beam epitaxy. The magnetic and magnetotransport properties of Ga1–xMnxSb random alloys are strongly dependent on Sb/Ga flux ratio. Clear square-like hysteresis loops were observed for Sb/Ga flux ratios between 4.60 and 5.25. The coercive field and negative magnetoresistance increase with decreasing Sb/Ga flux ratio, while the Curie temperature remains constant at approximately 23 K, with no systematic dependence on the hole density. In contrast, the Curie temperatures for the GaSb:Mn digital alloys with different Mn surface coverages depend significantly on the Sb/Ga flux ratio, and it is also directly correlated with the hole density. 相似文献
15.
Magnetic properties and heat generation characteristics of a bio-compatible ceramic Mg1+xFe2–2xTixO4 system have been investigated as an implant material for the magnetic induction hyperthermia. Curie temperature (Tc) of the ceramic decreases with increasing x; and become Tc, 350 K at x ç0:35 and, 315 K at x ç 0:38; which is suitable Curie temperature for implant material. The temperature of ceramic as a function of time under the high frequency alternating magnetic field is self-controlled at Tc.The surface temperature of a powder injection sphere cancer model, which was a mixture of the agar phantom and the ceramic powder implant, and the temperature distribution around the sphere set in the pure agar phantom matrix have been measured. The result is in good agreement with calculation using a finite element method (FEM). It was found that the temperature distribution inside of the sphere and the minimum quantity of Mg1+xFe2–2xTixO4 necessary for hyperthermia could be estimated by the FEM calculation. 相似文献
16.
The temperature dependences of the resistivity R(T) and the thermoelectric power α(itT) under different hydrostatic pressuresP for the system La{2-x}BavCuO4, 0.11 ≤ x < -1.6, are reported and interpreted as evidence for strong electron coupling to oxygen vibrations along the CuO-Cu
bond axes of the CuO2 sheets. The sensitivity of the transport properties to the bending Φ of the (180‡-Φ) Cu-O-Cu bond angle and their insensitivity
to long-range magnetic order indicate that the segregation into hole-rich and magnetic stripe domains is driven primarily
by electron-lattice interactions and not by electron-electron interactions alone. 相似文献
17.
In this work, the dispersion mechanisms affecting the electric transport in CuIn1−xGaxSe2 (CIGS) thin films grown by a chemical reaction of the precursor species, which are evaporated sequentially in two and three-stage processes are analyzed. It was found, through conductivity and Hall coefficient measurements carried out as functions of temperature, that the electrical conductivity of the CuIn1−xGaxSe2 films is affected by the transport of free carriers in extended states of the conduction band as well as for variable range hopping transport mechanisms, each one predominating in a different temperature range. 相似文献
18.
Crystalline arsenic telluride exists in two stable phases. The monoclinic α-phase transforms to rhombohedral β-phase under high pressure. The electronic, optical and transport properties of the two phases has been investigated using full potential linear augmented plane wave (LAPW) + local orbitals (lo) scheme, in the framework of DFT with generalized gradient approximation (GGA). We present the energy bands, density of states and optical properties like the complex dielectric functions and absorption coefficients. From the dynamic dielectric constant, the structural anisotropy for the monoclinic α-phase is clearly observed, whereas the longitudinal and transverse components are almost identical for the β-phase. The optical absorption profiles clearly indicate that β-phase has possibility of greater multiple direct and indirect interband transitions in the infrared and visible regions compared to the α-phase. The rhomohedral phase which has the Bi2Te3 type structure has the possibility of thermoelectric properties, therefore transport properties like electrical and thermal conductivities, Seebeck and Hall coefficients etc. are also calculated. Good agreements are found with the available experimental results. 相似文献
19.
Ying Wang Xuefeng Guo Wenpeng Yang Jianxin Zhang 《Materials Science & Technology》2017,33(15):1811-1818
In this paper, the effects of Sr, Sb, Sr+Sb and Sn on Mg2Si reinforcement phases in an Mg–Al–Zn–Si alloy are studied, and the structures and characteristics of Mg2(SixSn1?x) phases are analysed with first-principle calculations. The results show that the coarse eutectic Mg2Si can be refined by modifying processes with Sr, Sb, and their combination. When alloying with Sn, a new reinforcement phase Mg2(SixSn1?x) forms by a substitution reaction, instead of Mg2Si. Calculations indicate that Mg2(SixSn1?x) has a certain percentage of covalent bonds, which ensure it has sufficient hardness to act as a reinforcement phase. Calculated results for physical parameters, such as the bulk modulus and shear modulus, indicate that an Mg2(SixSn1?x) intermetallic exhibits greater ductility than Mg2Si.Highlights
The coarse eutectic Mg2Si can be refined by modifying processes.
A new phase Mg2(SixSn1?x) forms by substitution reaction during solidification.
Mg2(SixSn1?x) has certain covalent bound percentage.
Mg2(SixSn1?x) has better plasticity than that of Mg2Si.
20.
Single crystals of Zn1-xMnxTe were prepared by vertical Bridgman crystal growth method for different concentrations of Mn. Chemical analysis and reflectivity
studies were carried out for compositional and band structure properties. Microscopic variation in composition between starting
and end compounds was observed from EDAX analysis. Linear dependence of fundamental absorption edgeE
0as a function of Mn concentration (x) was expressed in terms of a straight line fit and a shift in E0 towards higher energy was observed in reflectivity spectra of Zn1-xMnxTe. 相似文献