Torque and magnetization measurements on the heavy fermion superconductor cesium cobalt indium.

摘要

We performed out-of-plane torque measurements on CeCoIn5 heavy fermion single crystals. Our results show large paramagnetism in this material in the normal state. We determined anisotropy parameter from the reversible part of the vortex signal. We found that anisotropy parameter is magnetic field and temperature dependent, which provides evidence that the picture in this unconventional superconductor is not a simple single band scenario.;Magnetization measurements were performed to investigate the mixed-state thermodynamics of CeCoIn5 in the presence of Zeeman effect. We successfully separated the paramagnetic and vortex contributions. We found that the paramagnetic magnetization is unusual and it has a non-linear magnetic field dependence, while the susceptibility Xp in the mixed state increases with increasing field. We concluded that the H dependence of Xp is a result of the fact that heavy electrons contribute to both superconductivity and paramagnetism and the Zeeman effect is large in this material.;We performed in-plane torque measurements on single crystals of CeCoIn5. We found that the mixed state four-fold symmetry and the peak positions in the irreversible torque point unambiguously towards dxy wave symmetry of the superconducting gap.;Angular dependent resistivity measurements were performed on single crystals of CeCoIn5. We found that the resistivity curves scale with the perpendicular field component Hcos theta, which is a result of flux-flow dissipation.