Pj. King et al., THE SCALING OF THE CURRENT-VOLTAGE CHARACTERISTICS OF THE YBA2CU3O7-Y2BACUO5 COMPOSITES, Phase transitions, 42(3-4), 1993, pp. 207-229
We have investigated features in the current voltage (I-V) characteris
tics of YBa2Cu3O7:Y2BaCuO5 composite sinters which indicate the occurr
ence of a second-order phase transition. For each sinter composition s
imilar families of characteristics are found for a wide range of magne
tic fields. The relation between V and I is seen to be of the form V =
f(I, xi(B, T)) where a single parameter xi contains all of the field
and temperature dependence. The locus of points in the B, T plane for
which xi(B, T) is a constant have been examined, and a low field and a
high field regime have been identified. Samples of different composit
ion show families of I-V characteristics which scale onto one another
in a simple way, hence we are led to suppose the V = f(I, xi(B, T, p))
where p is the dilution fraction. Data taken at temperatures below th
e phase transition agrees well with a simple scaling picture of dissip
ation close to a second order phase transition, with exponents which a
re independent of magnetic field and composition. Above the transition
, however, the behaviour is more complex.