Title :
Flux pinning in neutron irradiated YBa2Cu3O 7-x
Author :
Lessure, H.S. ; Simizu, S. ; Baumert, B.A. ; Sankar, S.G. ; McHenry, M.E. ; Maley, M.P. ; Cost, J.R. ; Willis, J.O.
Author_Institution :
Carnegie Mellon Univ., Pittsburgh, PA, USA
fDate :
3/1/1991 12:00:00 AM
Abstract :
Identical polycrystalline samples of YBa2Cu3O7-x have been irradiated with fast neutrons (E>0.1 MeV) in eight steps between 0 and 2.1×10 18 n/cm2. Notable irradiation effects include a Tc depression of nearly 2 K at the highest fluence and large improvements in the critical current density for fields from 0-9 T and temperatures from 4-80 K. Critical currents approaching 2×107 A/cm2 are observed for optimally irradiated materials at 5 K (in zero field), while at 77 K J c(0 kOe) approaches 5×105 A/cm2. Irradiation is seen to take a nearly equilibrium magnetization curve at 77 K and broaden it to a significantly hysteretic curve. A substantial shift in the effective pinning potential as a function of current density is inferred from magnetic relaxation measurement at H=1 T. This is the first such measurement in which systematically increased activation energies for flux creep (as a function of current density) are noted
Keywords :
barium compounds; critical current density (superconductivity); flux creep; flux pinning; high-temperature superconductors; magnetic hysteresis; magnetic relaxation; magnetisation; neutron effects; superconducting transition temperature; yttrium compounds; Tc depression; activation energies; critical current density; effective pinning potential; flux creep; high temperature superconductivity; hysteretic curve; irradiation effects; magnetic relaxation measurement; nearly equilibrium magnetization curve; neutron irradiated YBa2Cu3O7-x; polycrystalline samples; Critical current; Critical current density; Current density; Current measurement; Density measurement; Energy measurement; Flux pinning; Magnetic materials; Neutrons; Temperature;
Journal_Title :
Magnetics, IEEE Transactions on
