Pressure-induced anomalous magnetism and unconventional superconductivity in CeRhIn 5 : 115 In-NQR study under pressure

We report {sup 115}In nuclear-quadrupole-resonance (NQR) measurements of the pressure (P)-induced superconductor CeRhIn{sub 5} in the antiferromagnetic (AF) and superconducting (SC) states. In the AF region, the internal field H{sub int} at the In site is substantially reduced from H{sub int}=1.75kOe at P=0 to 0.39 kOe at P=1.23GPa, while the Neel temperature slightly changes with increasing P. This suggests that either the size in the ordered moment M{sub Q}(P) or the angle {theta}(P) between the direction of M{sub Q}(P) and the tetragonal c axis is extrapolated to zero at P{sup *}=1.6{+-}0.1GPa at which a bulk SC transition is no longer emergent. In the SC state at P=2.1GPa, the nuclear spin-lattice relaxation rate {sup 115}(1/T{sub 1}) has revealed a T{sup 3} dependence without the coherence peak just below T{sub c}, giving evidence for the unconventional superconductivity. The dimensionality of the magnetic fluctuations in the normal state is also discussed.