  REBa$_{2}$Cu$_{3}$O$_{x}$ films can achieve remarkably high critical current
density values by the incorporation of insulating nanoparticles. A particular
interesting case concerns BaZrO$_{3}$ (BZO) nanorods, whose strongly correlated
effect is seen at high temperatures. Here we investigate the field, temperature
and angular dependence of the critical current density over a wide temperature
range from 4.2 K to 77 K, and magnetic fields up to 31 T. We show that the
correlated c-axis pinning of BZO nanorods becomes progressively less obvious at
lower temperature. Indeed at 4.2 K and fields up to 31 T, the only correlated
pinning is for fields parallel to the film plane. We interpret the change as
being due to significant contributions from dense but weak pins that thermal
fluctuations render ineffective at high temperatures but which become strong at
lower temperatures.
