Resistive transitions of the new superconductor MgB_(2) are carried out under magnetic fields from 0 to 8 T.It is found that the irreversibility field Hirr(T)and the upper critical field Hc2(T)obtained are very close ...Resistive transitions of the new superconductor MgB_(2) are carried out under magnetic fields from 0 to 8 T.It is found that the irreversibility field Hirr(T)and the upper critical field Hc2(T)obtained are very close to those determined in the magnetic measurement.By using the Arrhenius activation lawρ=ρ0exp(-U/kBT),the activation barrier U has been determined by the low dissipation part of R(T)curves.It is found that U■kBT manifests a very weak thermal activation and thermal fluctuation effect.This may further indicate that the flux dynamics near Hirr(T)is induced by strong quantum fluctuation and tunneling of vortices.展开更多
基金Supported by the Ministry of Science and Technology of China(NKBRSF-G19990646)the National Natural Science Foundation of China under Grant No.19825111.
文摘Resistive transitions of the new superconductor MgB_(2) are carried out under magnetic fields from 0 to 8 T.It is found that the irreversibility field Hirr(T)and the upper critical field Hc2(T)obtained are very close to those determined in the magnetic measurement.By using the Arrhenius activation lawρ=ρ0exp(-U/kBT),the activation barrier U has been determined by the low dissipation part of R(T)curves.It is found that U■kBT manifests a very weak thermal activation and thermal fluctuation effect.This may further indicate that the flux dynamics near Hirr(T)is induced by strong quantum fluctuation and tunneling of vortices.
