The effective activation energy of one HgBaCaCuO 1223 superconductor as a function of current density was extracted from the magnetic relaxation measurements below 30K,and found to obey a power law.We also obtained ef...The effective activation energy of one HgBaCaCuO 1223 superconductor as a function of current density was extracted from the magnetic relaxation measurements below 30K,and found to obey a power law.We also obtained effective activation energy as a function of current density from the magnetic hysteresis loops(M-H).The data sets for the M-H loops at different temperatures overlap each other,and all fall on the smooth U_(eff)(J,0)curve based solely on the magnetization relaxation measurements.This indicates that the field dependence of magnetic critical current density is determined by the flux creep via nonlinear effective activation energy at low temperatures.展开更多
The rate equation for flux motion in high-T_(c) superconductors is extended to take the contribution of field sweep into account in this work.It is shown that the time and field sweep rate(H)dependence of magnetizatio...The rate equation for flux motion in high-T_(c) superconductors is extended to take the contribution of field sweep into account in this work.It is shown that the time and field sweep rate(H)dependence of magnetization are equivalent approaches to the study of flux creep properties in high-T_(c) superconductors.The agreement of the effective activation energy Ueff(J)extracted from the time relaxation and that from magnetic hysteresis loops measurements on a melt-textured YBa2Cu3O6+x sample supports this extended rate equation for flux motion in high temperature superconductors.展开更多
This paper studies a new electron irradiation effect of the formation,movement and growth of stacking fault in YBa_(2) Cu_(3) O_(6+x).The energy of electron irradiation is about 160keV.It would be a promising way to e...This paper studies a new electron irradiation effect of the formation,movement and growth of stacking fault in YBa_(2) Cu_(3) O_(6+x).The energy of electron irradiation is about 160keV.It would be a promising way to enhance the density of pinning centers.展开更多
Magnetic hysteresis loops and magnetization relaxation of a zone-melted Y Ba_(2)Cu_(3)O_(6+x) sample were measured by superconducting quantum interference device(SQUID)at temperature from 4.5 to 70K.The logarithmic be...Magnetic hysteresis loops and magnetization relaxation of a zone-melted Y Ba_(2)Cu_(3)O_(6+x) sample were measured by superconducting quantum interference device(SQUID)at temperature from 4.5 to 70K.The logarithmic behavior of niagnetic decay at 4.5 K and the gritdua,l deviation as the temperature is increased deinon-stra.ted the important role of nonlinea.r current density dependence of effective flux pinning potential U(J)in high temperature supcrconductors.展开更多
The effect of slow neutron irradiation at a low Auence of about 10^(8)n/cm^(2) on the microstructures of Bi-2223 polycrystalline samples was observed by transmission electron microscopy.By comparative study of the def...The effect of slow neutron irradiation at a low Auence of about 10^(8)n/cm^(2) on the microstructures of Bi-2223 polycrystalline samples was observed by transmission electron microscopy.By comparative study of the defect structures in a given area in one sample,we get evidence for the flux pinning enhancement by low Auence slow neutron irradiation.展开更多
We measured the time decay of the magnetic moment of high Tc supercon-ductors YBa_(2)Cu_(3)O_(7-δ);ceranic samples and found the memory effect which has hitherto been reported ouly in single crystals.The temperature ...We measured the time decay of the magnetic moment of high Tc supercon-ductors YBa_(2)Cu_(3)O_(7-δ);ceranic samples and found the memory effect which has hitherto been reported ouly in single crystals.The temperature and feld ranges,especialy the memory time are diferent from those of the latter.We believed that the memory phenomenon in ceramic samples at liquid nitrogen temperature can only be understood in a combined picture of both fux creep and glass behaviour.展开更多
基金Supported by the National Center for Research and Development on Superconductivity of ChinaNational Foundation for Doctoral Education.
文摘The effective activation energy of one HgBaCaCuO 1223 superconductor as a function of current density was extracted from the magnetic relaxation measurements below 30K,and found to obey a power law.We also obtained effective activation energy as a function of current density from the magnetic hysteresis loops(M-H).The data sets for the M-H loops at different temperatures overlap each other,and all fall on the smooth U_(eff)(J,0)curve based solely on the magnetization relaxation measurements.This indicates that the field dependence of magnetic critical current density is determined by the flux creep via nonlinear effective activation energy at low temperatures.
基金Supported by the National Center for Research and Development on Superconductivity of Chinathe Foundation for Doctoral Education。
文摘The rate equation for flux motion in high-T_(c) superconductors is extended to take the contribution of field sweep into account in this work.It is shown that the time and field sweep rate(H)dependence of magnetization are equivalent approaches to the study of flux creep properties in high-T_(c) superconductors.The agreement of the effective activation energy Ueff(J)extracted from the time relaxation and that from magnetic hysteresis loops measurements on a melt-textured YBa2Cu3O6+x sample supports this extended rate equation for flux motion in high temperature superconductors.
基金Supported by the National Center for Research and Development of Superconductivity of Chinathe Foundation for Doctoral Education.
文摘This paper studies a new electron irradiation effect of the formation,movement and growth of stacking fault in YBa_(2) Cu_(3) O_(6+x).The energy of electron irradiation is about 160keV.It would be a promising way to enhance the density of pinning centers.
基金Supported by the National Center for Research and Development on Superconductivity of Cliinathe Foundation for Doctoral Education.
文摘Magnetic hysteresis loops and magnetization relaxation of a zone-melted Y Ba_(2)Cu_(3)O_(6+x) sample were measured by superconducting quantum interference device(SQUID)at temperature from 4.5 to 70K.The logarithmic behavior of niagnetic decay at 4.5 K and the gritdua,l deviation as the temperature is increased deinon-stra.ted the important role of nonlinea.r current density dependence of effective flux pinning potential U(J)in high temperature supcrconductors.
基金Supported by the National Center for Research and Development on Superconductivity of China,and the Foundation for Doctoral Education。
文摘The effect of slow neutron irradiation at a low Auence of about 10^(8)n/cm^(2) on the microstructures of Bi-2223 polycrystalline samples was observed by transmission electron microscopy.By comparative study of the defect structures in a given area in one sample,we get evidence for the flux pinning enhancement by low Auence slow neutron irradiation.
基金Supported by the National Center of China for Research and Development on Supereonductivity.
文摘We measured the time decay of the magnetic moment of high Tc supercon-ductors YBa_(2)Cu_(3)O_(7-δ);ceranic samples and found the memory effect which has hitherto been reported ouly in single crystals.The temperature and feld ranges,especialy the memory time are diferent from those of the latter.We believed that the memory phenomenon in ceramic samples at liquid nitrogen temperature can only be understood in a combined picture of both fux creep and glass behaviour.
