Magnetic and Superconducting Phase Diagramof Heavy Fermion Superconductors Ce_1-xTh_xCu_2.2Si₂–Cu NMR and NQR Study

The magnetic and superconducting phase diagram of Th-doped Ce1-xTh(x)Cu2.2Si2 has been established by Cu NMR and NQR technique and is compared with that of CeCu2.02Si2. Static magnetic ordering with T(N) = 2.4 K and 4.5 K for x = 0.08 and 0.12, respectively, is evidenced by a pronounced broadening of the Cu-63-NQR and -NMR spectra and a pronounced anomaly in the specific heat. In contrast, for the lightly Th-doped compounds with x less-than-or-equal-to 0.064, there has been observed neither a signature of a broadening of the NQR and NMR spectra nor an anomaly of the specific heat, but a dramatic reduction of the NMR and NQR intensities below a temperature ranging from 0.9 K to 1.3 K upon increasing Th-content. It is emphasized that the unusual "magnetic transition" found in undoped and lightly Th-doped CeCu2.2Si2 should be distinguished from the static magnetic ordering in the heavily Th-doped systems