Field-Induced Antiferromagnetism and Upper Critical Field in Pressure-Induced Superconductor CeRhIn5

Abstract

An antiferromagnet CeRhIn 5 is well known to be changed into a superconductor by applying pressure P . Its electronic state is also clarified to be changed at the critical pressure P c ≃2.5 GPa under magnetic fields. We measured the low-temperature electrical resistivity of CeRhIn 5 in magnetic fields up to 17 T and at pressures up to 2.45 GPa, and constructed phase diagrams. At P = 2.45 GPa, which is close to P c ≃2.5 GPa, there are four kinds of phases, namely, the paramagnetic, superconducting, superconducting and antiferromagnetic, and antiferromagnetic phases in the temperature vs magnetic field phase diagram. The antiferromagnetic phase is found to be induced in the superconducting phase under magnetic fields and expanded in magnetic fields higher than the upper critical field in superconductivity. Interestingly, the anisotropy of the upper critical field in CeRhIn 5 is found to be different from that in a similar non-magnetic heavy-fermion superconductor CeCoIn 5 , revealing the anisotropic paramag...