V. Bekeris et al., HYSTERETICAL TEMPERATURE-DEPENDENCE OF AC SUSCEPTIBILITY IN GRANULAR HIGH-T-C SUPERCONDUCTORS, Physica. C, Superconductivity, 234(1-2), 1994, pp. 49-56
The AC susceptibility, chi(AC)(T), with superimposed DC magnetic field
, H-a(DS), has been measured as a function of temperature in bulk sint
ered LaSrCuO, for zero-field cooled (ZFC) and field-cooled (FC) sample
s. Results are analyzed within Kim's critical-state model extended to
a granular superconductor, where the role of grains is to determine th
e temperature-dependent effective permeability, mu(eff)(T), and the ef
fective intergranular local field, H-j(eff)(H-a(DC), T), which depends
on the applied field, H-a(DC) and the thermal and magnetic history, a
ccounting for the observed hysteresis. A method to determine field-ind
ependent intergranular critical-state parameters (critical current at
zero field and temperature-dependent density of pinning forces as well
as mu(eff)(T)) and the proper scaling of H-j(eff)(H-a(DC), T) for ZFC
and FC conditions is described. The calculated AC susceptibility for
the whole temperature range for both magnetic conditions reproduces th
e main features of the experimental results.