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1.
A. P. Gerashchenko K. N. Mikhalev S. V. Verkhovskii Yu. V. Piskunov A. V. Anan’ev K. A. Okulova A. Yu. Yakubovskii L. D. Shustov 《Journal of Experimental and Theoretical Physics》1999,88(3):545-551
Data on the NMR line shifts, the spin-lattice relaxation rate of 63Cu and 17O nuclei, and the spin-spin relaxation rate of 63Cu are obtained for Tl2Ba2CaCu2O8−δ
(T
c
=112 K) in the normal and superconducting states. The hyperfine constants at the copper and oxygen atoms in a CuO2 plane are estimated from an analysis of the temperature dependence of the Knight shift. The temperature-dependent behavior
of the long-and short-wavelength parts of the dynamic spin susceptibility is discussed by modeling an antiferromagnetic Fermi
liquid. The possible relation between the characteristics of the spin-fluctuation spectrum and the superconducting transition
temperature is analyzed for the oxide investigated.
Zh. éksp. Teor. Fiz. 115, 991–1001 (March 1999) 相似文献
2.
A. Tsukada K. E. Luna R. H. Hammond M. R. Beasley J. F. Zhao S. H. Risbud 《Applied Physics A: Materials Science & Processing》2011,104(1):311-318
We report the effects of growth conditions on the superconducting properties of FeSe films epitaxially grown on LaAlO3 substrates by pulsed laser deposition (PLD). Customary materials characterization techniques [X-ray diffraction (XRD), in-situ
X-ray photoelectron spectroscopy (XPS), in-situ ultra-violet photoelectron spectroscopy (UPS), and scanning electron microscopy
(SEM)] revealed the films had a c-axis oriented tetragonal structure with lattice constants dependent on the growth temperature (varied from 100 to 600°C).
The standard four-point probe method was used to measure the resistivity and superconducting transitions. Films grown at 400–550°C
showed a clear superconducting onset but no zero resistance down to 2 K. The highest superconducting onset temperature (TconsetT_{\mathrm{c}}^{\mathrm{onset}}) of 8 K was observed in films grown at 500°C and the onset temperature was clearly correlated to the ratio of the lattice
constants (c/a). As the thickness of the FeSe films increased from 27 nm to 480 nm, TconsetT_{\mathrm{c}}^{\mathrm{onset}} also increased as the strain in the system was relaxed. 相似文献
3.
利用固态反应法制备了名义成分为FeTe的合金, 采用X射线粉末衍射技术和Rietveld全谱拟合分析方法测定了其相组成和晶体结构. 研究表明,主相为Fe1.08Te,空间群为P4/nmm,点阵参数 a = 3.8214(3) Å, c = 6.2875(3) Å, Z = 2, Fe原子占据2a和2c晶位, Te原子占据2c晶位. 利用脉冲激光沉积技术制备的FeTe薄膜超导转变起始温度为13.2 K,零电阻温度为9.8 K.
关键词:
FeTe
Rietveld结构精修
超导薄膜 相似文献
4.
The positive muon spin relaxation method is applied to probe magnetic ordering in the superconducting phase of a high quality
single crystal of La2−xSrxCuO4−σ (0.11≤x≤0.14). The well characterized crystal ofx=0.11 (T
c=34.5 K) with nearly complete flux exclusion exhibits spin freezing at 8K(T
f) with significant spin fluctuation up to 20 K. The onset of spin fluctuation andT
f decrease against increasingx towardsx=0.15, suggesting an existence of a magnetic phase boundary aroundx whereT
c becomes maximum. 相似文献
5.
V. G. Grebinnik V. N. Duginov V. A. Zhukov S. Kapusta A. B. Lazarev V. G. Olshevsky V. Yu. Pomjakushin S. N. Shilov I. I. Gurevich B. F. Kirillov E. P. Krasnoperov B. A. Nikolsky A. V. Pirogov A. N. Ponomarev V. A. Suetin A. I. Morozov 《Hyperfine Interactions》1991,63(1-4):241-247
High temperature superconductors HoBa2Cu3O7−δ (T
c
≅93 K), Ho0.5Y0.5Ba2Cu3O7−δ (T
c
≅93 K) and ErBa2Cu3O7−δ (T
c
≅95 K) were investigated by the zero-field μSR-technique. The muon spin depolarisation rate connected with the fluctuation
frequency of rare-earth ion magnetic moments was measured. It was found that the samples with holmium show a fast increase
of the muon spin depolarisation rate at temperatures below 20 K, while in ErBa2Cu3O7−δ the depolarisation rate remains low in the whole temperature region studied (4.2 K-270 K). The sharp difference between the
behaviours of the muon spin depolarisation rate may be explained by the difference between the ground state of Ho3+ and Er3+ ions in the crystalline field of the lattice. 相似文献
6.
X-ray and resistivity measurements on YBa2Cu3O7−δ
(1-2-3) samples show that for the same but low oxygen concentration,δ⋍0·55, no superconducting transition down to 4·2 K is observed for the tetragonal phase samples while the orthorhombic phase
shows aT
c ∼ 31 K. The effect of oxygen concentration onT
c is isolated.T
c=91±1 K has, however, been observed continuously for the normal oxygen annealed samples,δ⋍0·07. The experimental results suggest strongly the necessity of the 1-2-3 compound to be in the orthorhombic phase for the
superconducting mechanism to be operative. 相似文献
7.
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
8.
A. P. Gerashenko K. N. Mikhalev S. V. Verkhovskii T. V. D’yachkova A. P. Tyutyunnik V. G. Zubkov 《Applied magnetic resonance》2001,21(2):157-163
Nuclear magnetic resonance (NMR) spectra and nuclear spin-lattice relaxation rateT
1−1 of11B have been measured in superconducting polycrystalline MgB2 with 7cons = 39.5 K. It is shown that (T
1T−1 and the Knight shiftK
s are independent of temperature and nearly isotropic aboveT
c. Both of these quantities are decreased gradually in going to the superconducting state. According to NMR data the density
of states near the Fermi level is flat at the scale of about 500 K. Some conclusions on the orbital content of the density
of states at the Fermi level were drawn and compared with the results of the band structure calculations. 相似文献
9.
V. Yu. Yushankhai 《Hyperfine Interactions》1989,50(1-4):775-779
On the basis of current theoretical views on the critical phenomena in isotropic Heisenberg ferromagnets the power temperature
behavior Λ=c(τ)λ0τ-w has been derived for the muon spin relaxation rate Λ as π-T
c
−1
(T-T
c
) → 0+. It is shown that the crossover from an exchange critical regime to a dipolar one is accompanied not only with the change
in the critical exponentw in the above law, but also with the reduction of the coefficientc(π). A comparison with the temperature behaviour of the inverse nuclear relaxation timet
R
−1
measured in the PAC experiment is carried out. 相似文献
10.
It is well known that the superconducting transition temperature of high-T
c
cuprates depends on the number of CuO2 planes in the unit cell. The multilayer structure implies the possibility of interlayer hopping. Under the assumption that
the interlayer hopping can be specified by the parameter t
⊥(k) = t
⊥(cos(k
x
) − cos(k
y
))2, the quasiparticle excitation spectrum for the bilayer cuprate in the superconducting state has been determined in the framework
of the t − t′ − t″ − t
⊥ − J* model using the generalized mean-field approximation. It turns out that the interlayer hoppings does not create any additional
mechanism of the Cooper paring and does not lead to an increase in T
c
. The splitting of the upper Hubbard quasiparticle band attributed to the interlayer hoppings is manifested as two peaks in
the doping dependence of the superconducting transition temperature at temperatures below the maximum T
c
value for a single-layer cuprate. It has been found that antiferromagnetic interlayer correlations suppress the interlayer
splitting. This probably leads to the common doping dependence of T
c
for both single-layer and bilayer cuprates. 相似文献
11.
Silver-clad tapes of highT
c Bi-Pb-Sr-Ca-Cu-O superconductors have been fabricated through the powder-in-tube method. The critical current density, J
c
, of a thick tape was 534 A.cm−2 (77 K, 0 T). Subsequent rolling and sintering of the tapes led to a gradual decrease inJ
c, instead of the expected increase. This was caused by the microcracks developed in the core material by a rather drastic
reduction during the rolling of the tapes. A modified and well controlled rolling technique, on the other hand, resulted in
much improvedJ
c values. Repeated rolling and sintering resulted in a good grain alignment and no microcracks were observed. In the present
studies, maximumJ
c of 1846 A.cm−2 (77 K, 0 T) and 2.43 × 104 A.cm−2 (4.2 K, 0 T) have been obtained Optimization of the processing and sintering parameters are expected to lead to still higherJ
c values. 相似文献
12.
C. Camerlingo H. Huang B. Ruggiero M. Russo E. Sarnelli G. Testa 《Il Nuovo Cimento D》1994,16(12):2019-2024
Summary An analysis of superconducting transport properties and magnetic behaviour of d.c. SQUIDs employing YBCO bicrystal grain boundary
junctions (GBJs) has been performed. GBJs have been obtained by deposition of ac-axis-oriented YBCO film on a SrTiO3 bicrystal substrate by ICM sputtering technique. Experimental measurements on a YBCO d.c. SQUID with a misorientation angle
θ=20° are reported. The SQUID shows a critical temperatureT
c∼89 K and a high critical current densityJ
c∼3·106 A/cm2 atT=4.2 K. Current-voltage characteristics are close to the behaviour predicted by the resistively shunted junction (RSJ) model
and the temperature dependenceJ
c(T) shows a linear behaviour at small reduced temperatures and a depressedJ
c value close toT
c. High-quality flux-voltage curves have been found upT=87 K over a large range of magnetic field. The high reproducibility and the good control of transport properties by the variation
of θ make YBCO bicrystal GBJs very useful for applications in electronics.
Paper presented at the ?VII Congresso SATT?, Torino, 4–7 October 1994. 相似文献
13.
I. A. Makarov S. G. Ovchinnikov E. I. Shneider 《Journal of Experimental and Theoretical Physics》2012,114(2):329-342
The influence of interlayer hoppings on the superconducting transition temperature (T
c) in bilayer cuprates has been studied. The parameter of hopping between layers is expressed as t
⊥(k) = t
⊥(cos(k
x
) − cos(k
y
))2 and treated as a small perturbation for the states of two CuO2 planes described by the t-t′-t″-J* model. In the generalized mean field approximation for dx2 - y2{d_{{x^2} - {y^2}}} symmetry of the superconducting gap, neither the interlayer hopping or exchange interaction, nor the pair hopping between
CuO2 layers provides an additional mechanism of Cooper pair formation or an increase in T
c. In the concentration dependence of T
c, the bilayer splitting of the upper Hubbard band of quasi-holes is manifested as two peaks with temperatures slightly lower
than the maximum T
c for a single-layer cuprate. Interlayer antiferromagnetic spin correlations suppress bilayer splitting. 相似文献
14.
S. L. Bondarev V. N. Knyukshto S. A. Tikhomirov A. N. Pyrko 《Optics and Spectroscopy》2003,94(6):928-933
The spectral-luminescent properties and electronic-level structure of a derivative of oxotetrahydrobenzo[c]phenanthridine—3,3-dimethyl-1,2,3,4-tetrahydrobenzo[c]phenanthridine-1-one
(DTP)—in polar and nonpolar solutions are studied by the luminescence and picosecond spectroscopy techniques at 293 and 77
K. It is shown that DTP exhibits ππp* fluorescence only in polar proton-containing methanol, ethanol, and n-propanol and that this fluorescence is associated with a chromophore + alcohol complex. Solutions of DTP in n-propanol and the nonpolar mixture methylcyclohexane + toluene (6:1) at 77 K display ππp* phosphorescence with a quantum yield
ΦPh=0.1, a lifetime τPh=1.9 s, and a frequency of the 0-0 transition equal to 21550 cm−1. The fact that DTP fluorescence is absent in aprotic solvents and exists in alcohols is explained by the inversion of the
energy levels of the S
ππ* and T
n
π* states, as a result of which the energy level of the fluorescing S
ππ* state in alcohol becomes the lowest. The picosecond spectra and kinetics of the inducedS
n
(ππ*) ← S
1(π π*) and T
k
(ππ*) ← T
1(ππ*) absorption made it possible to estimate the lifetime of the S
1(ππ*) state of DTP in n-propanol at 293 K (20±10 ps) and the position of the triplet-triplet absorption peak (495 nm).
__________
Translated from Optika i Spektroskopiya, Vol. 94, No. 6, 2003, pp. 993–998.
Original Russian Text Copyright ? 2003 by Bondarev, Knyukshto, Tikhomirov, Pyrko. 相似文献
15.
B. Gorshunov C.A. Kuntscher P. Haas M. Dressel F.P. Mena A.B. Kuz'menko D. van der Marel T. Muranaka J. Akimitsu 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,21(2):159-161
Far-infrared reflectivity studies on the polycrystalline intermetallic compound MgB2 with a superconducting transition temperature T
c
= 39 K were performed at temperatures 20 K to 300 K. We observe a significant raise of the superconducting-to-normal state reflectivity
ratio below 70
cm
-1
, with a maximum at about 25-30
cm
-1
, which gives a lower estimate of the superconducting gap of 2Δ(0)
≈ 3-4 meV.
Received 7 March 2001 and Received in final form 18 April 2001 相似文献
16.
M. K. Aliev G. R. Alimov T. M. Muminov B. A. Olimov Kh. I. Turkmenov I. Kholbaev L. I. Leonyuk R. F. Rumi 《Physics of the Solid State》1999,41(1):11-14
Y1Ba2Cu3O7−x
single crystals are investigated near T
c
≈92 K in fields 0<H⩽9 kOe using a modified ESR spectrometer. The temperature modulation method is used for the first time, together with the
traditional magnetic modulation method, to detect microwave responses in single crystals. Superconducting-transition peaks
shifted relative to one another in temperature and differing in shape are observed in the temperature dependence of the corresponding
signals ∂R/∂H and ∂R/∂T (R — microwave absorption). The evolution of these peaks as a function of the field and the angle π between H and the c axis of the single crystal is traced. It is shown that the difference in the temperature dependences of the derivatives ∂R/∂H and ∂R/∂T is due to the broadening of the superconducting transition characteristic of HTSCs.
Fiz. Tverd. Tela (St. Petersburg) 41, 14–17 (January 1999) 相似文献
17.
I. G. Gogidze P. B. Kuminov A. V. Sergeev A. I. Elant’ev E. M. Men’shchikov E. M. Gershenzon 《Technical Physics》1998,43(10):1193-1198
A new type of fast detector is proposed. The operation of the detector is based on the change induced in the kinetic inductance
of NbN and YBa2Cu3O7−δ
superconducting films by nonequilibrium quasiparticles produced by electromagnetic radiation. The speed of a NbN detector
is essentially temperature-independent and is less than 1 ps. A model based on the Omen-Scalapino scheme describes well the
experimental dependence of the voltage-power sensitivity of a NbN detector on the modulation frequency of the radiation. A
low equilibrium quasiparticle density and a high quantum yield give detecting power D*=1012W−1 · cm · Hz1/2 at temperature T=4.2 K and D*=1016 W−1 · cm · Hz1/2 at temperature T=1.6 K. The time constant of the low-temperature YBaCuO induction detector is determined only by the electron-phonon interaction
time τ
e-ph
d
in the nodal regions.
Zh. Tekh. Fiz. 68, 63–69 (October 1998) 相似文献
18.
We have investigated the superconducting properties of the Bi1.7 Pb0.3Sr2Ca2−xCe
x
Cu3O10+δ system with x=0.00, 0.02, 0.04, 0.08 and 0.1 by X-ray diffraction and magnetic susceptibility. The substitution of Ce for Ca has been found
to drastically change the superconducting properties of the system. X-ray diffraction studies on these compounds indicate
decrease in the c-parameter with increased substitution of Ce at Ca site and volume fraction of high T
c (2 : 2 : 2 : 3) phase decreases and low T
c phase increases. The magnetic susceptibility of this compound shows that the diamagnetic on set superconducting transition
temperature (onset) varies from 109 K to 51 K for x=0.00, 0.02, 0.04, 0.08 and 0.1. These results suggest the possible existence of Ce in a tetravalent state rather than a trivalent
state in this system; that is, Ca2+ → Ce4+ replacement changes the hole carrier concentration. Hole filling is the cause of lowering T
c of the system. 相似文献
19.
G. Fabritius G. Flik J. Golczewski D. Herlach G. Jünemann M. Krenke K. Maier A. P. Pathak H. Rempp A. Seeger W. Sigle E. Widmann D. W. Cooke 《Hyperfine Interactions》1986,31(1-4):229-234
By means of π+/μ+ channelling, positive pions (π+) implanted intoTa, Mo, andW are investigated up to high temperatures. A striking observation is that the channelling effect disappears in a rather narrow
temperature interval centred at 0.26 (Ta) to 0.51 (W) of the melting temperature. From studies of π+ trapping by oxygen atoms inTa estimates for the low-temperature π+ diffusivity inTa [D
π(23K)=1.4·10−10±0.3 m2s−1,D
π(47K)=5.7·10−10±0.3 m2s−1] as well as for the binding enthalpy of π+ to 0 atoms (H
B=7·10−2 eV) have been obtained. The diffusion data are in reasonable agreement with the theory of phonon-assisted tunnelling. 相似文献
20.
G. Kalai Selvan M. Kanagaraj S. Esakki Muthu Rajveer Jha V. P. S. Awana S. Arumugam 《固体物理学:研究快报》2013,7(7):510-513
We investigate the external hydrostatic pressure effect on the superconducting transition temperature (Tc) of new layered superconductors Bi4O4S3 and NdO0.5F0.5BiS2. Though the Tc is found to have a moderate decrease from 4.8 K to 4.3 K (dTconset/dP = –0.28 K/GPa) for Bi4O4S3 superconductor, the same increases from 4.6 K to 5 K (dTconset/dP = 0.44 K/GPa) up to 1.31 GPa followed by a sudden decrease from 5 K to 4.7 K up to 1.75 GPa for NdO0.5F0.5BiS2 superconductor. The variation of Tc in these systems may be correlated to an increase or decrease of the charge carriers in the density of states under externally applied pressure. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献