Abstract

An overdoped YBa2Cu3O7 single crystal was studied by SQUID and torque magnetometry in order to investigate the temperature dependence of the anisotropy parameter close to the transition temperature Tc (0.87Tc<T<Tc). Angle-dependent torque measurements were performed and analyzed with the widely used Kogan model [ Phys. Rev. B 38 7049 (1988)] as well as with an extended model by Hao and Clem [ Phys. Rev. Lett. 67 2371 (1991)], taking into account the influence of the vortex cores on the magnetization. Both approaches yield similar results, with an out-of-plane anisotropy parameter around 6.5 which slightly increases with decreasing temperature, and a temperature independent in-plane anisotropy parameter γab=1.12(5).