Anisotropy of Iodine Intercalated Bi2212 Single Crystals by Magnetic Torque

The magnetic torque of iodine intercalated Bi2Sr2CaCu2O8+δ (I-Bi2212) single crystals has been measured under magnetic fields up to 8 kOe in the temperatures from 4.2 to 100 K. The anisotropy parameter for the 1-Bi2212 determined by London model is smaller than that for the pure Bi2Sr2CaCu2O8+δ (Bi2212). A sharp peak C1 due to the intrinsic pinning and an extra peak C2 due to the dimensional crossover of the pancake vortex are observed in the magnetic field direction dependence of the torque. The reduced temperature at which the peak C1 appears with decreasing temperature is T/Tc=0.82, which is lower than T/Tc=0.97 for the pure Bi2212. The dimensional crossover field for the I-Bi2212 obtained from the peak C2 is larger than that for the pure Bi2212. According to these results, it is concluded that the iodine intercalation causes the enhancement of interlayer coupling.