Muon spin relaxation has been measured in ${\mathrm{CeCoGe}}_{3-x}{\mathrm{Si}}_x$ at the magnetic/nonmagnetic boundary compositions of $x=1.2\mathrm{}$ and $x=1.5\mathrm{}$. Both the alloys are found to exhibit an ordered region and a disordered region. At $x=1.2\mathrm{}$, short-range magnetic ordering is observed below 0.86 K in the ordered region. The disordered region is paramagnetic and the muon spin-lattice relaxation rate ${\lambda }_2$ in this region displays non-Fermi-liquid (NFL) spin dynamics, i.e., the power law ${\lambda }_2\propto T^{0.72}$ which shows the formation of Griffiths phase. ${\lambda }_2$ in the $x=1.5\mathrm{}$ alloy displays logarithmic (NFL) scaling below 1 K, in agreement with the theory of a $T=0\mathrm{}\mathrm{K}$ magnetic transition.

• Received 1 March 2000

DOI:https://doi.org/10.1103/PhysRevLett.88.046402