We report on muon spin rotation studies of the noncentrosymmetric heavy fermion antiferromagnet CeRhSi3. A drastic and monotonic suppression of the internal fields, at the lowest measured temperature, was observed upon an increase of external pressure. Our data suggest that the ordered moments are gradually quenched with increasing pressure, in a manner different from the pressure dependence of the Néel temperature. At 23.6 kbar, the ordered magnetic moments are fully suppressed via a second-order phase transition, and T(N) is zero. Thus, we directly observed the quantum critical point at 23.6 kbar hidden inside the superconducting phase of CeRhSi3.

Zero field (ZF) and transverse field (TF) muon spin relaxation and rotation (μ SR) experiments have been carried out in the Cd-doped heavy fermion superconductor CeCoIn5 to investigate its superconducting state. The ZF-μ SR results in CeCo (In0.97 Cd0.03)5 revealed that no spontaneous magnetic field was induced below its superconducting transition temperature (Tc), indicating no evidence for time reversal symmetry breaking. The muon Knight shifts obtained from TF-μ SR measurements decrease significantly below Tc, consistent with a spin-singlet state as in the parent compound CeCoIn5, which is a d-wave superconductor. © 2008 Elsevier B.V.