Magnetic-Properties and Remanent Magnetization Studies of YBA2CU3O7 Thin-Films (original) (raw)
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MAGNETIZATION AND HYSTERESIS PROPERTIES OF SUPERCONDUCTING YBa2Cu3O7–x THIN FILMS
High Tc Superconductors, 1989
Magnetic properties of textured superconducting YBa,Cu,O, x thin films prepared by r.f. reactive sputtering are reported. Initial magnetization curves and hysteresis loops have been measured at several temperatures for fields parallel and perpendicular to the film. Hysteresis losses have been studied as a function of maximum applied field. The results are consistent with the Bean model of the critical state and with the H,, values reported for single crystals. 0022.5088/89/$3.50 ((1 Elsevier Sequoia/Printed in The Netherlands
Physica C Superconductivity
By means of high-sensitivity capacitance torque magnetometers we have measured the superconducting current Js and the dynamic magnetic-moment relaxation of YBazCu307 and YBazCu4Os films of typically 100 nm thickness at temperatures between 2 K and Tc in magnetic fields up to 6 T. For the measurements of the dynamic relaxation rate Q==-d lnjs/d ln(dBc/dt) magnetic-field sweep rates were varied between 0.5 and 40 mT/s. At low fields (typically 0.5 T) the dynamical relaxation rate exhibits a plateau at Q~ 0.06 in YBa2Cu307 and 0.04 in YBa2Cu4Os. At high fields (Be=/toHc-~ 6 T) the plateaus have completely disappeared and Q increases almost linearly with increasing temperature. At all fields a sharp increase up to Q~ 1 is observed when the irreversibility line is approached.
Critical current, magnetization relaxation and activation energies for YBa2Cu3O7 and YBa2Cu4O8 films
Physica C: Superconductivity, 1994
By means of high-sensitivity capacitance torque magnetometers we have measured the superconducting current Js and the dynamic magnetic-moment relaxation of YBazCu307 and YBazCu4Os films of typically 100 nm thickness at temperatures between 2 K and Tc in magnetic fields up to 6 T. For the measurements of the dynamic relaxation rate Q==-d lnjs/d ln(dBc/dt) magnetic-field sweep rates were varied between 0.5 and 40 mT/s. At low fields (typically 0.5 T) the dynamical relaxation rate exhibits a plateau at Q~ 0.06 in YBa2Cu307 and 0.04 in YBa2Cu4Os. At high fields (Be=/toHc-~ 6 T) the plateaus have completely disappeared and Q increases almost linearly with increasing temperature. At all fields a sharp increase up to Q~ 1 is observed when the irreversibility line is approached.
Critical current, magnetization relaxation and activation energies for YBa2Cu307 and YBa2Cu408 films
By means of high-sensitivity capacitance torque magnetometers we have measured the superconducting current Js and the dynamic magnetic-moment relaxation of YBazCu307 and YBazCu4Os films of typically 100 nm thickness at temperatures between 2 K and Tc in magnetic fields up to 6 T. For the measurements of the dynamic relaxation rate Q==-d lnjs/d ln(dBc/dt) magnetic-field sweep rates were varied between 0.5 and 40 mT/s. At low fields (typically 0.5 T) the dynamical relaxation rate exhibits a plateau at Q~ 0.06 in YBa2Cu307 and 0.04 in YBa2Cu4Os. At high fields (Be=/toHc-~ 6 T) the plateaus have completely disappeared and Q increases almost linearly with increasing temperature. At all fields a sharp increase up to Q~ 1 is observed when the irreversibility line is approached.
Temperature dependence of flux pinning in YBa2Cu3Ox
Physica C: Superconductivity, 1989
Magnetization versus applied field data have been taken up to 5 T over a wide temperature range from 10 K to 77 K for polycrystalline YBa,Cu,O, with x=6.98 and x=6.62. The intragrain critical current density has been calculated based on the magnetization measurements. The observed temperature dependence of the flux pinning behavior in the x= 6.98 sample indicates a new pinning mechanism in the intermediate temperature region, whose strength increases linearly with the applied field above certain field values. The experimental results also suggest that the twin boundary pinning is active only in the low temperature
Physica C: Superconductivity, 1994
We study the angular dependence of the magnetic properties of Y-Ba-Cu-O thin films irradiated with 0.86 GeV Pb and 5 GeV Xe ions. For the Pb irradiated samples the critical current has a maximum when the direction of the external magnetic field coincides with the direction of the columnar defects induced by the irradiation. For the Xe irradiated samples such anisotropy in the critical current was not found. The pinning force density obeys a scaling law of the form bP(1-b)q, where b= Hcxt/Hirr(T), and H~,t and Hi,~ are the external and the irreversibility fields, respectively. The exponents p and q depend on the type and direction of the irradiation.
Defects in YBa2Cu3O7−δ thin films studied by magneto-optics
Physica C-superconductivity and Its Applications, 1996
By means of the magneto-optical Faraday effect, flux-density distributions are observed in laser-ablated YBa2Cu30 7_ 8 thin films. The samples investigated are found to contain numerous defects of two different classes; (1) extended linear defects of weakly superconducting material and (2) small non-superconducting particles. The influence of these defects on the flux distributions is analyzed in detail using the concept of discontinuity lines of the currents [Th. Schuster et al. Phys. Rev. B 49 (1994) 3443]. The magneto-optical flux patterns clearly reveal that an application of a critical-state model to calculate the critical current density from magnetization data is impossible when a sample contains such defects. It is shown that even in the best samples the flux fronts are not homogeneous but consist of a large number of defect-induced parabolic flux plumes.
Superconductor Science and Technology, 2005
Nanodot arrays of Y 2 O 3 were dispersed in thin films of YBa 2 Cu 3 O 7−δ (YBCO) by growing alternating layers of these two species using a pulsed laser deposition method. As a result, critical current density J c both in applied magnetic field and self-field is enhanced by as much as an order of magnitude, along with a significant increase in the irreversibility field H irr . High-resolution scanning transmission electron microscopy (STEM) and Z -contrast STEM show that the nanoparticles are crystalline and coherent with the YBCO matrix. Whereas in most other studies pinning has been attributed to the strain fields around the nanoparticles, in this case pinning may actually be due to the nanoparticles themselves, since the delineation between the two species is very sharp and STEM reveals no discernible strain fields in the superconducting material around the nanoparticles.
Magnetic pinning effects of epitaxial LaxSr1−xMnO3 nanostructured thin films on YBa2Cu3O7−δ layers
Journal of Applied Physics, 2012
The present paper presents the effects of a nanostructured, ferromagnetic La 1Àx Sr x MnO 3 (LSMO) thin film on the pinning characteristics of an epitaxial YBa 2 Cu 3 O 7 (YBCO) thin film deposited on top. Ordered arrays of LSMO grains were obtained upon growing the film on a terraced (001) SrTiO 3 substrate. The analyses of magnetic measurements revealed the presence of a complex vortex pinning mechanism within the YBCO film. With respect to a reference single YBCO layer, an additional pinning potential was observed. Its temperature evolution suggests that a magnetic pinning mechanism is responsible for improved pinning characteristics in the high temperature and field region. Based on the morphology of the underlying LSMO buffer, a strong pinning force is expected to arise due to the anti-dot formations, where a high magnetization gradient exists.