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1.
Abstract We made the superconductor of Bi2Sr2CaCu2Oγ by the solid state reaction. According to the results of measurement by infrared spectrophotometer with the varying of wave number from 4000 to 400 cm?1. We discovered three infrared absorption peaks at room temperature, i.e., peak A1 at 500–550 cm?1, peak A2 at 800–840 cm?1 and peak A3 at 1370–1420 cm?1. We find that peak A1 is due to impure phase, peak A2 is related with the crystal structure and peak A3 is caused by the vibration of the atom layers of calcium. 相似文献
2.
The critical current densities (J
c) have been measured at 77K in high pressure oxygen sputtered thin films of YBa2Cu3O7−x
superconductor using the non-resonant rf absorption technique. High values ofJ
c (∼ 105 A/cm2) are observed in these relatively large area (∼ 1·2 cm2) films. 相似文献
3.
Abstract We have measured the electrical resistance R of a sintered, two-phase, high-TC superconductor with the nominal composition BiSrCaCu2Ox, as a function of T and p. We find d(lnR)/dp ? -0.06 GPa?1 at 295 K, while dTC/dp is 2.5 K/GPa for the phase with Tc ? 76 and 2 K/GPa for that with TC ? 106 K. 相似文献
4.
Abstract Optical absorption spectra of TeO2 crystals, irradiated at room temperature by up to 2·1018 cm?2 10-MeV electrons and subsequently annealed to 575K, are studied. The dependence of Urbach absorption edge parameters in TeO2 on the electron beam fluence is discussed. The irradiation-induced near-edge broad (2.5–3.5eV) absorption band is shown to be related to oxygen vacancies, annealing at 475–525K. 相似文献
5.
Silver clad wires of highT
c superconductor Y1Ba2Cu3O7−x
have been fabricated through the powder metallurgy technique. The reacted wires show a midpointT
c of 84K. A critical current density of 26·4 A cm−2 (77K, 0T) is obtained in these wires. The wires, however, turn complete normal only at a current density of 280 A cm−2. The reasons for low critical current density obtained in these wires are discussed. 相似文献
6.
With the vibrating-reed technique, the internal friction (IF) Q−1 is measured for sing-phase (Hg0.66Pb0.34)Ba2Ca2Cu3O8+x superconductor as a function of temperature at low applied magnetic field up to 0.5 T and as a function of frequency at normal state temperatures. An IF peak associated with flux motion can be found below TC. The IF peak becomes higher and shifts towards lower temperature with increasing magnetic field. In addition an IF peak is found near 200 K. By scaling analysis we have demonstrated that the internal friction around the peak temperature can be collapsed into a single curve, indicating that the IF peak below TC is originated from a phase transition associated with a vortex glass transition and a structural phase transition occurs at around 200 K in the superconductor. 相似文献
7.
I. Felner I. Nowik E. R. Bauminger U. Yaron D. Hechel 《Hyperfine Interactions》1992,70(1-4):1163-1166
57Fe Mössbauer spectroscopy, magnetic susceptibility and powder x-ray-diffraction measurements were used to study superconductivity and magnetic order in YBa2(Cu1?xFex)4O8+δ. Tc is decreasing with x, disappearing for x>xc≈0.04. For xc iron substitutes Cu, predominantly in the Cu(1) site exhibiting a single quadrupole Mössbauer spectrum at 90 K. For x>xc magnetic order is observed in the Cu(2) site, TN=380 (5) K for x=0.1 and Heff (Cu(2), 4.2 K)=510(2) kOe. However, the most surprising discovery is that for x=0.025, for which Tc=27(2) K, the Fe in the Cu(1) site orders magnetically at TN=30(2) K and Heff (Cu(1), 4.2 K)=461(2) kOe. The coexistence and competition between superconductivity and magnetic order in the Cu(1) and Cu(2) sites in YBa2Cu4O8 are discussed in terms of the previously observed phase diagrams for Y1?xPrxBa2(Cu1?yFey)3Oz. 相似文献
8.
We report on the electrical resistivity and far-infrared reflectance measurements of LaO1?xFxFeGe samples. Furthermore, we introduce a new method to probe the energy gap and determine its value. The onset transition temperature was 22.8 K for x = 0.13, and a clear anomaly was observed at 90 K in the ρ(T) curve for x = 0.11 with Tc = 20.6 K. We clearly observed the phonon-suppressed feature in reflectance spectra where F-doping caused a strong suppression of a peak at 200 cm?1. The energy gap above Tc, 2Δ = 2.10 meV, was determined from the measured spectra based on the changes in reflectivity by F-doping. 相似文献
9.
The temperature dependence of the upper critical fields, Hc2(T), are presented for (La1-xGdx)Sn3 and (La1-xTmx)Sn3. For samples with nearly the same Tc, Hc2(T) of the Tm-doped LaSn3 samples are always larger than those for the Gd-doped samples. The results are interpreted in terms of crystalline electric field splitting of magnetic levels of the Tm3+. Pure LaSn3 is found to be a Type I superconductor. 相似文献
10.
N. IbrahimA.K. Yahya S.S. RajputS. Keshri M.K. Talari 《Journal of magnetism and magnetic materials》2011,323(16):2179-2185
La0.85−xSmxAg0.15MnO3 (x=0−0.2) ceramics were prepared using the conventional solid-state synthesis method to investigate the effect of Sm3+ substitution on magnetic and electrical transport properties. Magnetic susceptibility versus temperature measurements showed all samples exhibit ferromagnetic to paramagnetic transition with Curie temperature, Tc decreasing from 283 K (x=0) to 164 K (x=0.2) with increasing Sm3+. The observed slope in susceptibility, χ′ versus temperature curves below Tc indicates the possible presence of FM and AFM phases in the metallic region. In addition, a deviation from the Curie-Weiss law above Tc in 1/χ′ versus T curves indicates the existence of a Griffith's phase in the x=0.05−0.2 samples due to the Sm3+ ion substitution. The Griffith temperature, TG was found to decrease from 295 K (x=0.05) to 229 K (x=0.2). Electrical resistivity measurements of the samples in zero field showed transition from metallic behavior to insulating behavior as the temperature was increased. For x=0, two metal-insulator, MI transition peaks were observed at Tp1=282 K and at Tp2=250 K. Both peaks shifted to lower temperatures with the increase in Sm3+. The relative resistivity of the first peak to the second peak decreases with increasing Sm3+ for x>0.05 while at x=0.2 the Tp1 peak was strongly suppressed. Magnetoresistance, MR was observed to weaken with Sm3+ substitution. The metallic region of the ρ(T) curve of the x=0−0.15 samples was fitted to the model of electron-electron and electron-magnon scattering while the insulating region was fitted to the variable range hopping, VRH model. The resistivity behavior indicated that the substitution of Sm3+ weakened the double exchange process and enhanced the Jahn-Teller effect. Our results indicated that the Tp1 peak is strongly related to the double-exchange mechanism while the Tp2 peak is suggested to originate from magnetic inhomogeneity. 相似文献
11.
N. Momono T. Nakano A. Eida K. Chida Y. Miura M. Oda M. Ido 《Czechoslovak Journal of Physics》1996,46(Z3):1233-1234
The electronic specific heat Cel was studied at T≤10K on Ga- and Zn-doped La2−xSrxCuO4 (0.16≤x≤0.22). In pure La2−xSrxCuO4 (0.16≤x≤0.22), the Cel at T<Tc contains only a T2 component but no T-linear one, which is peculiar to a clean d-wave superconductor. Partial substitution of Ga or Zn for Cu
changes the T2-term of Cel into a quite different one described by the sum of a T-linear and a nearly T3 term. The coefficient of the T-linear term, γ, markedly increases with Zn-or Ga-content. The λ/λN vs. Tc/Tco relation for Zn-doped samples with x≥0.2 is in good agreement with the theoretical curve for resonant impurity scattering
in a d-wave superconductor, while those for Ga-doped samples and for Zn-doped samples with x<0.2 deviate slightly from the
theoretical curve. Such a deviation will be discussed in relation to the change in the magnetic properties of the present
system caused by impurity-doping. 相似文献
12.
Dielectric properties of ceramic samples of Sr1−x
PbxTiO3 solid solutions for x varying from 0 to 0.3 have been studied. The ferroelectric phase transition in this system has been established to persist
down to x=0.005. Within the x values of 0.002 to 0.05, the ferroelectric transition temperature is shown to follow the relation T
c=A(x−x
c)1/2, with A=440 K and x
c=0.002.
Fiz. Tverd. Tela (St. Petersburg) 39, 714–717 (April 1997) 相似文献
13.
T. Mertelj D. Mihailovic 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,23(3):325-327
Photoinduced IR absorption measurements are reported on WO3. A photoinduced midinfrared small polaron peak centered at 4800 cm-1 (0.59 eV) was observed. The data were analyzed in the framework of the photon-assisted small-polaron hopping theory and briefly
compared to previously published infrared absorption measurements in WO3 and photoinduced IR absorption measurements in high T
c
cuprates.
Received 20 April 2001 and Received in final form 13 July 2001 相似文献
14.
ABSTRACTThe blue phase of YBa2Cu3O7- δ (YBCO) family, Y2Cu2O5 (Y202) nanoparticles were prepared and doped into (YBCO) superconductor and the effect of doping on critical current density and critical temperature was investigated. Y202 nanoparticles with particle sizes of 47, 107 and 206?nm were prepared by a sol–gel combustion method and added into the YBCO superconductor by 0.5–2?wt.%. XRD and scanning electron microscope measurements were used to characterize the samples. The measurement of critical current density at 77?K revealed that the doped superconductors had larger critical current density compared to the undoped superconductors. For a fixed dopant concentration, by increasing the size of nanoparticles, the Jc was increased. For the samples including 0.5?wt.% of nanoadditives, Jc was higher. The highest critical current density of 137?A/cm2 was measured for the superconductors containing 0.5?wt.% of 206?nm Y202 nanoparticles. Also, by increasing the nanoparticles concentration, the Tc was reduced. 相似文献
15.
P. Bonville J. A. Hodges C. Vaast E. Alleno C. Godart L. C. Gupta Z. Hossain R. Nagarajan G. Hilscher H. Michor 《Zeitschrift für Physik B Condensed Matter》1996,101(4):511-520
166Er Mössbauer absorption spectra have been recorded in the superconductor ErNi2B2C (T c = 10 K), in zero field and in the temperature range 1.4 K–40 K. The spectra in the magnetically ordered phase (T N ? 5.5 K) are characteristic of an incommensurate magnetic structure with a maximum Er3+ moment of 8.2 μB. We show that the magnetic transition is first order, with a small temperature range where magnetically ordered and paramagnetic domains coexist. The analysis of the magnetic and quadrupolar hyperfine interactions below and above T N suggests that the Er3+ ground doublet is close to |J = 15/2; J z = ± 1/2 > and shows that there is a low lying (? 10 K) excited doublet. The measured Er3+ electronic relaxation rate 1/T1 shows an anomaly at 10 K (T c suggesting that the conduction electrons that are exchange coupled to the 4f spin take part in the formation of the superconducting state. We also present specific heat data for Er x Y1 ? x Ni2B2C and Er0.2Lu0.8Ni2B2C which also evidence a low lying doublet and from which we propose a modified (improved) Er3+ crystal field level scheme (0, 9, 62, 71, 73, 181, 212 and 216 K) where the energies of the higher levels are consistent with published neutron scattering data. 相似文献
16.
《Solid State Communications》1987,64(9):1209-1211
The high critical temperature superconductor YbBa2Cu3O7−x has been studied over the range 0.05 to 95K using 170Yb Mössbauer absorption spectroscopy. Magnetic ordering occurs within the Yb3+ sublattice at 0.35K. The saturated magnetic moments are 1.7μB. At all temperatures the hyperfine parameters show the presence of distributions attributed to some disordering of the oxygen vacancies. 相似文献
17.
The compound (NH3)xNaRb2C60 (x ~ 1.6) has been studied by1H nuclear magnetic resonance. The proton line shows no shift at any temperature, while lineshape analysis of the low-temperature (30 K) spectra reveals the presence of a Knight shift interaction of pure anisotropic nature, whose amplitude has been estimated. Relaxation measurements show a single-exponential recovery of the magnetization at all investigated temperatures and fields. A Korringa behavior is observed below 65 K and a clear Hebel-Slichter coherence peak is detected just below Tc. The London penetration depth can be estimated from the line broadening observed below Tc, which yields λ ≈ 825 nm. 相似文献
18.
U. Staub L. Soderholm S. Skanthakumar S. Rosenkranz C. Ritter W. Kagunya 《Zeitschrift für Physik B Condensed Matter》1997,104(1):37-43
Neutron diffraction experiments were performed to study the magnetic ordering of the Tb+3 sublattice in the high-T c superconductor Pb2Sr2Tb1?x Ca x Cu3O8 (x = 0.5) and the undoped parent compound (x = 0). For the parent compound, a quasi two dimensional (2D) phase with a finite antiferromagnetic correlation along the c-direction and a three dimensional phase with ferromagnetic correlation along the c-direction were found. The coexistence of the two phases is likely to be related to structural imperfections such as stacking faults, strains, oxygen disorder or cation vacancies. The superconductor with a superconducting transition temperature of T c = 71K exhibits a quasi 2D magnetic ordering of the Tb sublattice with a finite ferromagnetic correlation along the c-direction. The correlation lengths along the c-direction for the quasi 2D phases are 32 and 26Å for x = 0 and 0.5, respectively. The magnetic saturation moments are with 9.1 and 8.8 μ B in excellent agreement with our mean-field crystal-field calculations. 2D short range correlation could be observed up to about 8T N and is described by a Lorentzian distribution of magnetic intensity perpendicular to the 2D rod in reciprocal space. 相似文献
19.
The longitudinal and transverse relaxation rates of 19F nuclei in Pr2CuO4−x
Fx (x=0.20) samples are measured at high temperatures (150 K<T<600 K). A feature is found in the temperature dependence of the relaxation rates at temperature T′≅300 K. The magnetic properties of the electronic superconductor Pr2CuO4−x
Fx as a possible system with a stripe ordering of carriers and spins are discussed.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 4, 328–332 (25 February 1997) 相似文献
20.
R. M. Vlasova B. V. Petrov V. N. Semkin E. I. Zhilyaeva S. A. Torunova R. N. Lyubovskaya 《Physics of the Solid State》2013,55(9):1913-1919
The polarized reflectance spectra of microcrystals of the new organic superconductor (EDT-TTF)4[Hg3I8]1 ? x (T c = 8.1 K for x = 0.027; T c = 7 K at 0.3 kbar for x = 0.019) have been investigated in the spectral region of 700–6000 cm?1 (0.087–0.740 eV) at temperatures ranging from 10 to 300 K. A quantitative analysis of the spectra has been performed in the framework of the phenomenological Drude and Drude-Lorentz dispersion models, as well as in the framework of the theoretical “phase phonon” model that takes into account the interaction of free electrons with intramolecular vibrations. The effective mass of charge carriers m*, the width of the initial metallic π-electron band W, and the integral t of the electron transfer between the molecular π-orbitals of neighboring molecules have been determined. In the low-frequency range (700–1600 cm?1), the vibrational structure associated with intramolecular vibrations of the EDT-TTF molecule has been revealed. It has been shown that the most intense feature (ω = 1330 cm?1) of this structure is caused by the interaction of “quasi-free” electrons with intramolecular vibrations. 相似文献