Possible Evolution of Antiferromagnetism in Zn-Doped Heavy-Fermion Superconductor CeCoIn5

We have succeeded in growing single crystals of the heavy-fermion superconductor CeCo(In1−xZnx)5 with x ≤ 0.07. Measurements of specific heat, electrical resistivity, dc magnetization and ac susceptibility revealed that the superconducting (SC) transition temperature Tc decreases from 2.25 K (x = 0) to 1.8 K (x = 0.05) by doping Zn into CeCoIn5. Furthermore, these measurements indicate a development of a new ordered phase below To ∼ 2.2 K for x ≥ 0.05, characterized by the reduced magnetization and electrical resistivity in the ordered phase, and the enhancement of specific heat at To. This phase transition can be also recognized by the shoulder-like anomaly seen at Ho ∼ 55 kOe in the field variations of the magnetization at low temperatures, which is clearly distinguished from the superconducting critical fields Hc2 = 49 kOe for x = 0.05 and 42 kOe for x = 0.07. We suggest from these results that the antiferromagnetic (AFM) order is generated by doping Zn, and the interplay between the SC and AFM orders ...