Cooperative Behavior of the Random and Correlated Pinning in Er123 Films With Columnar Defects

The flux pinning behaviors for the heavy ion irradiated Er123 films are investigated based on the detailed J
_c
(B,T,θ) properties. The double peaks of F
_p
curves for B//c appear in case of the matching field of 0.3 T along c-axis and 1.7 T tilted from c-axis. In addition, the peaks on J
_c
(θ) at θ = 0°(B//c), which originate from the columnar defects, decrease with increasing magnetic field but increase again near the irreversibility field. We found that the cooperation model of the c-axis correlated and random pinning centers can describe the observed double peak behavior of F
_p
(B) and the angular dependence of J
_c
related to the correlated pinning.