Magnetic torque measurements on Bi2201 single crystal in high magnetic fields

The magnetic field direction dependence of the magnetic torque in the super conducting state of Bi2Sr1.65La0.35CuO6+delta (Bi2201) single crystal has b een measured in several static magnetic fields up to 200 kOe. The applied f ield dependence of the anisotropy parameter, gamma, defined by the square r oot of the effective mass ratio has been obtained by fitting the magnetic t orque curves at 17 K by means of the effective mass model. For Bi2Sr2CaCu2O 8+delta (Bi2212), the gamma values up to 210 kOe were reported previously. At each field, gamma for Bi2201 is larger than that for Bi2212. Since the g amma value decreases as the field increases both for Bi2201 and Bi2212, the reduction of gamma by the application of the high magnetic field is consid ered to be common for Bi-based layered superconductors.