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
Magnetic measurements have been carried out on partial melt(Tl_(0.5)Pb_(0.5))(Ba_(x)Sr_(0.8))_(2)Ca_(2)Cu_(3)O_(y)(x=0.1,0.2)(TI-1223)samples,which indicate that higher melting temperature and longer melting time can ...Magnetic measurements have been carried out on partial melt(Tl_(0.5)Pb_(0.5))(Ba_(x)Sr_(0.8))_(2)Ca_(2)Cu_(3)O_(y)(x=0.1,0.2)(TI-1223)samples,which indicate that higher melting temperature and longer melting time can be used to obtain Tl-1223 compound with better superconducting properties.On the contrary,introducing of Ba vacancy into Tl-1223 samples results in worse superconducting properties.At the end,the power law relationship between the critical current density and the applied field is explained by the flux creep model and the collective pinning theory.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
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.
文摘Magnetic measurements have been carried out on partial melt(Tl_(0.5)Pb_(0.5))(Ba_(x)Sr_(0.8))_(2)Ca_(2)Cu_(3)O_(y)(x=0.1,0.2)(TI-1223)samples,which indicate that higher melting temperature and longer melting time can be used to obtain Tl-1223 compound with better superconducting properties.On the contrary,introducing of Ba vacancy into Tl-1223 samples results in worse superconducting properties.At the end,the power law relationship between the critical current density and the applied field is explained by the flux creep model and the collective pinning theory.
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.
