Coexistence of Antiferromagnetism and Superconductivity near the Quantum Criticality in Heavy Fermion Compound CeRhIn$_5$

We report a study on the interplay between antiferromagnetism (AFM) and superconductivity (SC) in a heavy-fermion compound CeRhIn$_5$ under pressure $P=1.75$ GPa. The onset of the magnetic order is evidenced from a clear split of $^{115}$In-NQR spectrum due to the spontaneous internal field below the Neel temperature $T_N=2.5$ K. Simultaneously, bulk SC below $T_c=2.0$ K is demonstrated by the observation of the Meissner diamagnetism signal whose size is the same as in the exclusively superconducting phase. These results indicate that the AFM coexists homogeneously with the SC at a microscopic level.