Angular-dependent torque measurements on CeCoIn5 single crystals

Angular-dependent torque measurements were performed on single crystals of CeCoIn5, a heavy fermion superconductor (T-c0=2.3 K), in the temperature, T, range 1.9 K <= T <= 20 K and magnetic fields H up to 14 T. A large paramagnetic effect is found in the normal state. Torque measurements in the mixed state were also performed. The torque curves show sharp hysteresis peaks at theta=90 degrees (theta is the angle between H and the c-axis of the crystal), a result of intrinsic pinning of vortices. The anisotropy gamma equivalent to root m(c)/m(a) in the mixed state was determined from the reversible part of the vortex contribution to the torque signal using Kogan's model [Phys. Rev. B 38, 7049 (1988)]. The anisotropy gamma decreases with increasing magnetic field and temperature. The fact that gamma is not a constant points towards a multiband scenario in this heavy fermion material.