Search results for "DOP"
showing 10 items of 4870 documents
Universal relationship between the penetration depth and the normal-state conductivity in YBaCuO
1999
The absolute values of the conductivity in the normal state sigma_n and of the low temperature penetration depths lambda(0) were measured for a number of different samples of the YBaCuO family. We found a striking correlation between sigma_n and 1/lambda^2, regardless of doping, oxygen reduction or defects, thus providing a simple method to predict the superconducting penetration depth and to have an estimate of the sample quality by measuring the normal-state conductivity.
Microscopy studies of the surface of high-temperature superconductor films
1997
The surface morphology is studied by use of optical and electron microscopes with respect to production regime (rate and temperature of crystallization) of the 50 - 125 micrometer thick doped YBa 2 Cu 3 O 7 films obtained by Stokes sedimentation on SrTiO 3 ceramic substrate (size 20 mm by 5 mm by 0.5 mm) and firing in air or oxygen following the MTG procedure, performed in the gradient tube furnace. Evolution of thick film structure with regard to temperature and cooling rate is studied.
The effect of Fe doping on superconductivity in ZrRuP
2011
Abstract This work reports the structure and superconducting properties of the superconductor ZrRuP doped with Fe; the ZrRu 1− x Fe x P solid solution was investigated by means of X-ray powder diffraction, SQUID magnetometry and Mosbauer spectroscopy. It is shown that the modification of the superconducting properties by doping with Fe is similar to the effect of chemical pressure and that the Fe doped compounds do not show any magnetic ordering.
Vortex-system ordering during magnetisation measurements in YBa2Cu3O7−δ films at low temperatures
2007
Abstract Zero-field-cooling dc magnetisation relaxation measurements performed on optimally doped epitaxial YBa 2 Cu 3 O 7− δ films with the external magnetic field H oriented parallel to the c -axis reveal the ordering of the creeping vortex-system in the low temperature T domain, due to the macroscopic currents induced in the sample. This dynamic ordering manifests itself through the appearance of a maximum in the T variation of the normalised vortex-creep activation energy. The location of this maximum in the H – T plane describes a well-defined current induced order–disorder line. Our results suggest the absence of a static elastic vortex glass in disordered high-temperature superconduc…
Superconductivity suppression in Fe-implanted thin Al films
2005
At present, ion implantation into metallic systems is given increasing attention, aiming at achieving properties and functionalities of technologically valuable materials not easily available via conventional techniques. In our experiments thin Al films were implanted with Fe ions in order to find out how the superconductive properties of the metal can be modified at will. The purpose was twofold, viz., first, to study the basic physics of superconductivity in low-dimensional metallic structures doped with impurities. The second purpose was to apply ion implantation for the suppression of undesired superconductivity in aluminum widely used for fabrication of micro- and nanodevices operated …
Efficient electronic cooling in heavily doped silicon by quasiparticle tunneling
2001
Cooling of electrons in a heavily doped silicon by quasiparticle tunneling using a superconductor–semiconductor–superconductor double-Schottky-junction structure is demonstrated at low temperatures. In this work, we use Al as the superconductor and thin silicon-on-insulator (SOI) film as the semiconductor. The electron–phonon coupling is measured for the SOI film and the low value of the coupling is shown to be the origin of the observed significant cooling effect.
Magnetic ordering in Fe-doped Gd2 BaCuO5
1994
The structural and magnetic properties of iron-doped Gd2BaCuO5 have been studied by X-ray diffractometry, Mossbauer spectroscopy and susceptibility measurements. Mossbauer data on Gd2BaCu0.8Fe0.2O5 show that at room temperature Fe is not magnetically ordered, displaying hyperfine parameters similar to those generally assigned to Fe at Cu(2) sites in the GdBa2(Cu1−x; Fe; x; )3O7 superconductor. Susceptibility measurements demonstrate that Gd2BaCu1−x; Fe; x; O5 behaves like a three-dimensional antiferromagnet withT; N=11.9±0.1 K, independent ofx. The effective magnetic moment calculated within a mean field approximation is consistent with an ordering of the Gd sublattice.
Magnetic phase diagrams in heavy-fermion compounds
1990
Magnetic phase diagrams have been explored in heavy-fermion (HF) compounds by controlled changes of the stoichiometry (UCu4+xAl8−x), dopant concentration (Ce(Cu1−xNix)2Ge2) and magnetic field (CeCu2Si2). The results demonstr competition (i) between Kondo and RKKY interactions in the former two compounds and (ii) between HF superconductivity and some cooperative state, presumably HF band magnetism, in the latter.
Vortex–antivortex unbinding in oxygen-deficient YBa2Cu3O7− films
2007
Abstract In-plane zero-magnetic-field current–voltage ( I – V ) characteristics of oxygen-deficient YBa 2 Cu 3 O 7− δ films (7 − δ ∼6.5, 6.55, and 6.65) were thoroughly investigated. A good agreement with the quasi two-dimensional (2D) vortex–antivortex unbinding scenario was observed, similar to the behaviour of highly anisotropic Bi 2 Sr 2 CaCu 2 O 8+ δ films. The temperature variation of the I – V exponent allows the determination of the Berezinskii–Kosterlitz–Thouless transition temperature T KT at the superconducting Cu–O layer level, and the mean-field critical temperature T c0 . We found that both T KT and T c0 increase with increasing doping, and T c0 remains in the region of the …
Spectral broadening by spatial effects in X-ray microcalorimeters with superconducting absorber and NTD-Ge thermal sensor
2004
We discuss how the sensitivity to the position of absorption of the photons can affect the spectral resolution of X-ray microcalorimeters with superconducting Sn absorber and NTD-Ge thermal sensor. Data obtained through the computer simulations are reported for microcalorimeters with different geometries and phonon transmission probabilities at the interface between the absorber and thermistor.