Ya. Fedorov et al., CURRENT AND FIELD DISTRIBUTIONS IN SUPERCONDUCTING FILMS - DETERMINATION OF CRITICAL-CURRENT BY LOCAL-FIELD MEASUREMENT, Physica. C, Superconductivity, 217(1-2), 1993, pp. 63-72
The current J and magnetic field H distributions in a thin film have b
een calculated for arbitrary changes of the external field (H(e)). A j
oint solution of equations describing the field and current distributi
ons in three different states (Meissner, critical and mixed) taking in
to account a tangential field has been found. The decrease of the exte
rnal field leads to the appearance of the mixed state with a current l
ess than the critical one (J < J(c)). A simple method for deriving the
function J(c)(H) from the experimental dependence H(p)(H(e)) (H(p) =
the normal field in the centre of the film) has been suggested. An exa
mple given for a thin ceramic disk shows good agreement of magnetic an
d transport J(c) values at H(e) = 0. The hysteresis loops H(p)(H(e)) c
alculated on the basis of the functions J(c)(H) found for a ceramic di
sk and a thin film fitted well with the experimental data.