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1.
The thermal expansion of the a and c axes of lT-TaS2 and of the a axis of 2H-NbSe2 have been measured between 4 K and 360 K. Discontinuities in the lattice parameters of TaS2 were observed at the known charge density wave phase transitions near 200 K and 352 K, and a new transition was found near 283 K. These results are used to estimate the entropy changes occurring at the phase transitions. At the charge density wave onset temperature in NbSe2 we find an upper limit to any discontinuity in the a axis of 2 × 10-7 and to any discontinuity in the expansion coefficient of 3 × 10-7 K-1. 相似文献
2.
The transverse energy gap in 2H-NbSe2 has been measured using a Nb flat “point” contact tunneling technique. Its value of 1.15±0.07 milivolt yields a value of 3.78 for the ratio 2Δ(0)/kTc. 相似文献
3.
Resistance ratios of crystals of 2H-NbSe2 grown with and without iodine were measured over the temperature range 6K–40K. Iodine-free crystals had higher ratios than any NbSe2 previously reported and exhibited an abrupt anomaly at the onset of the charge density wave phase. All crystals displayed a cubic temperature dependence of their resistivities below 18K. 相似文献
4.
Angle-resolved photoemission measurements have been made on the metallic layer compound 2H-NbSe2. From the results, E vs k∥ dispersion curves have been obtained along two principal symmetry directions in the Brillouin zone. The experimental energy bands are found to be in good agreement with the results predicted by one-dimensional density of initial states along k⊥. 相似文献
5.
The magnetorestriction constants of CoS2 single crystal were measured by a capacitance method in a temperature range from liquid N2 to the Curie temperatures.The constants γ100 and γ111 are ?1.9 × 10?6 and 5.7 × 10?6 at liquid N2 temperature respectively, and the absolute values of the constants decrease monotonically with the increase of the temperature. The volume magnetorestriction constant δω/δH at 110 K in the ferromagnetic state is 6 × 10?10 Oe?1. 相似文献
6.
Heat capacity measurements recently reported on the compound HoAl2 show an unexplained peak at 20 K. Magnetic measurements on a single crystal of HoAl2 reveal the existence, at this temperature, of a first order reorientation of the holmium moment. 相似文献
7.
Angle-resolved photoemission spectra of 2H-NbSe2 are calculated on the one-step model with a single plane wave final state and within the constant matrix element approximation. The results are compared with the experimental spectra obtained for ?ω = 21.2 eV. It is found that the intensities of the observed peaks are predicted reasonably well by this model (especially by one-dimensional density of initial states along k?). 相似文献
8.
The free induction decay in CaF2 has been calculated with the help of the simple model. The method allows to clarify the physical nature and to compute some parameters of the nuclear magnetic resonance spectra. 相似文献
9.
C.H. Chen 《Solid State Communications》1984,49(7):645-647
In addition to the well-known 3a0 CDW superlattice, we have observed in 2H-NbSe2 a 2a0 superlattice and a well-defined elliptical contour of diffuse intensity between the 3a0 CDW spots. The 2a0 superlattice is indicative of a CDW formation through the saddle-point nesting on the Fermi-surface. 相似文献
10.
D.M. RoesslerW.A. Albers Jr. 《Journal of Physics and Chemistry of Solids》1972,33(2):293-296
The transverse and longitudinal optical phonon frequencies of tetragonal GeO2 have been determined by standard i.r. reflectance measurements employing classical dispersion theory to fit the experimental data. The static and high-frequency dielectric constants, as derived from the data, are also presented. 相似文献
11.
Magnetic measurements have been performed on a single crystal of DyNi2 in applied fields up to 135 kOe. In the ferromagnetic range (Tc = 25 K), the easy magnetization direction is [100] and the hardest one is [111]. Crystal field parameters have been determined from the field and temperature dependence of the magnetization measured along the three principal axes. A two-dimensional model has been used to take into account the rotation of magnetization towards the field. The deduced parameters are W = -0.8 K and x = 0.49. The corresponding anisotropy is very large: especially even a field of 135 kOe applied along a difficult magnetization axis cannot rotate the magnetization along this direction. 相似文献
12.
C. P. Yang Y. Z. Wang G. H. Wu B. P. Hu J. L. Wang Z. X. Wang Z. L. Jiang J. Zhu 《Solid State Communications》1999,110(12):667-671
A Y2Fe15Cr2 single crystal with the Th2Ni17-type structure has been prepared by the Czochralski method and investigated by means of Laue back-reflection, metallographic observation, X-ray diffraction, the singular point detection technique and magnetic measurements. A magnetohistory effect has been observed at a low temperature. Magnetization curves have been measured along the easy and hard directions in fields up to 6.5 T. The saturation magnetization and magnetocrystalline anisotropy field decrease with increasing temperature. The experimental magnetocrystalline anisotropy constant is in good agreement with the calculation results on first approximation. 相似文献
13.
With respect to the quasi-one dimensionality of single crystals of Nb3Se4, the electrical resistivity from 1.3 to 320 K and the critical magnetic field for superconductivity are measured. The resistivity along the Nb-chain direction is represented as a sum of a temperature independent and an intrinsic temperature dependent term. The temperature dependence of the intrinsic resistivity subjects to T3 form between 10 and 80 K above which it tends to a T linear form. The critical magnetic field is proportional to the temperature difference from the transition temperature. Its dependence is well fitted by the elliptical fluxoid model of Ginzburg-Landau theory. The ratio of the parallel and the perpendicular to the c-axis is 5.7. 相似文献
14.
Necessary conditions to observe NMR in wall-free metallic single crystal ferromagnets are formulated. 27Al NMR study in a magnetized single crystal GdAl2 confirms the validity of the preconditions. Improved resolution and control over orientation, both inherent to single crystal study, enable for the first time an angular dependent NMR measurement of hyperfine interaction in metallic ferromagnetic system. The significance of the measured hyperfine tensor ; ) is briefly discussed. 相似文献
15.
Magnetization measurements and neutron difrraction experiments were performed on a single crystal of ErGa2. Because of the strong crystal field effects a huge uniaxial anisotropy imposes the Er moments to be parallel to the c-axis of the hexagonal structure. We have shown that the transition from the antiferromagnetic structure to the ferromagnetic one, when the field is applied along c, occurs through an intermediate phase. Such a behaviour is very well accounted for using a simple Ising-like model which takes into account first and second nearest neighbours exchange interactions in the hexagonal layers. A quantitative determination of the crystalline electric field effects is also presented. 相似文献
16.
Single crystals of the spinel CoIn2S4 were grown by iodine vapor transport. The structural determination leads to Fd3m space group with Co2+ ions distribution between Oh (63%) and Td (37%) sites of the spinel structure. 相似文献
17.
本文通过分析不同几何配置下的偏振拉曼光谱对非线性光学晶体的晶格振动模式进行了研究. 首先根据因子群分析,将晶体的振动模按晶体对称群的不可约表示进行分类,其次测量了晶体在10–1600 cm-1范围内,不同几何配置下的偏振拉曼光谱,并在此基础上指认了晶体的晶格振动模式. 300 cm-1以下的振动峰,归结为晶体的外振动,来自[BiO6],[ZnO4],[BO4]和[BO3]原子基团的平动和转动;300cm-1以上为晶体的内振动,主要与Bi-O,和Zn-O键振动有关. 晶体拉曼光谱中最高振动频率达到1407 cm-1,被指认为[BO3]三角形中B-O键的伸缩振动,体现了[BO3]基团中高的电子非局域化程度.
关键词:
2ZnOB2O6单晶')" href="#">Bi2ZnOB2O6单晶
偏振拉曼光谱
振动模式 相似文献
18.
A superlattice is observed by electron diffraction in 2H-NbSe2 below the onset of charge density wave instability at 33.5 K. 相似文献
19.
Takasuke Matsuo Masami Tatsumi Hiroshi Suga Syûzô Seki 《Solid State Communications》1973,13(11):1829-1831
The heat capacity of SnCl2·2H2O single crystal was measured in the close vicinity of the phase transition temperature, Tc = 217.994 ± 0.01 K. Its anomalous part ΔC could be expressed as ΔC = A± ⊥ (T ? Tc)/Tc⊥-α±, where α+ = 0.492 ± 0.02, α- = 0.492 ± 0.02, A+ = 1.148 JK?mol?, and A- = 1.155 JK?mol?. A quasi-isothermal absorption of the enthalpy amounting to 34 J mol? was observed at Tc. 相似文献
20.
Results of the optical spectroscopy investigation of the cubic paramagnetic center Yb3+ ion in the Cs2NaYF6 single crystal are presented. The Stark level energies of the Yb3+ multiplets are established from absorption, luminescence and excitation luminescence spectra and the crystal field parameters are calculated. Information about the phonon spectra of Cs2NaYF6 crystals is obtained from the electron-vibrational structure of the optical absorption and luminescence spectra. 相似文献