We analyze the angular dependence of the irreversible magnetization of
YBa2Cu3O7 crystals with columnar defects inclined from the c-axis. At
high fields a sharp maximum centered at the tracks' direction is observed. At
low fields we identify a lock-in phase characterized by an angle-independent
pinning strength and observe an angular shift of the peak towards the c-axis
that originates in the material anisotropy. The interplay among columnar
defects, twins and ab-planes generates a variety of staircase structures. We
show that correlated pinning dominates for all field orientations.Comment: 9 figures, 4 figure
