We present a phase diagram for the antiferromagnetism and superconductivity in ${\text{Ce}}_2{\text{RhIn}}_8$ probed by In-NQR studies under pressure $\left(P\right)$. The quasi-two-dimensional character of antiferromagnetic spin fluctuations in the paramagnetic state at $P=0$ evolves into a three-dimensional character because of the suppression of antiferromagnetic order for $P>P_{\text{QCP}}\sim 1.36\text{GPa}$ (QCP: quantum critical point). Nuclear-spin-lattice relaxation rate $1/T_1$ measurements revealed that the superconducting order occurs in the $P$ range 1.36–1.84 GPa, with maximum $T_c\sim 0.9\text{K}$ around $P_{\text{QCP}}\sim 1.36\text{GPa}$.

• Received 9 October 2009

DOI:https://doi.org/10.1103/PhysRevB.80.184503