Interplay of Superconductivity, Antiferromagnetism, and Pauli Depairing in CeCoIn$_5$

TL;DR

This study investigates the complex interplay between superconductivity, antiferromagnetism, and Pauli depairing in CeCoIn5 by measuring magnetization and specific heat at ultra-low temperatures, revealing critical magnetic behaviors and phase transitions.

Contribution

It provides new insights into the magnetic and thermodynamic properties of CeCoIn5 under high magnetic fields along the c axis, especially regarding the absence of the Q-phase.

Findings

Sign change in magnetization at H_c2(0)

Fermi liquid behavior in the superconducting phase

Singularity in specific heat at H_c2(0)

Abstract

Low temperature magnetization M measurements down to 70~mK have been performed through the superconducting upper critical field H_c2 of CeCoIn5 with the field H parallel to the c axis of the tetragonal crystal. The crossing through the upper critical field H_c2(0) is marked by a sign change in the temperature dependence of M(T). A Fermi liquid law of the magnetization is observed in the superconducting phase while in the paramagnetic state above H_c2 a quasi-linear temperature dependence is obeyed. The specific heat below H_c2 is therefor dominated by the increase of \gamma (H), the linear term of the specific heat, and is marked by a singularity at H_{c2} (0). No indication of the so called Q-phase was observed below H_c2 (in contrast to the case with H applied in the basal plane).