Mixed-state hall effect in HgBa₂CaCu₂O_6+δ thin films with columnar defects

The mixed state Hall effect has been studied in high quality HgBa₂CaCu₂O_6+δ thin films while the pinning strength is modified by the irraddition of columnar defects. It has been shown that the pinning strength can be significantly improved by columnar defects.The sign reversal in Hall resistivity is found to be nearly independent of pinning while the scaling behavior between Hall resistivity (ρ_xy) and longitudinal resistivity (ρ_xx) is influenced by pinning. The exponent β in the scaling law ρ_xy ∼ ρ_xy^β decrease from 1.8 ± 0.1 to 1.5 ±_ 0.1 as pinning is enhanced. This results suggest that the sign reversal and the scaling are unrelated, and pinning is not the mechanism of the sign reversal.