  The electronic ground state in high-$T_{\rm c}$ cuprates where the
superconducting state is suppressed by Ni substitution has been investigated in
La$_{2-x}$Sr$_x$Cu$_{1-y}$Ni$_y$O$_4$ from the specific heat and muon spin
relaxation measurements. It has been found that the ground state changes from a
magnetically ordered state with the strong hole-trapping by Ni to a metallic
state with the Kondo effect of Ni with increasing hole-concentration. Moreover,
the analysis of the results has revealed that a phase separation into the
magnetically ordered phase and the metallic phase occurs around the boundary of
two phases.
