Systematic ${}^{63}\mathrm{Cu}$ NQR study of the stripe phase in ${\mathrm{La}}_{1.6-x}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ for $0.07<~x<~0.25$

We demonstrate that the integrated intensity of ${}^{63}\mathrm{Cu}$ nuclear quadrupole resonance (NQR) in ${\mathrm{La}}_{1.6-x}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ decreases dramatically below the charge-stripe ordering temperature $T_{\mathrm{charge}}.$ Comparison with neutron and x-ray scattering indicates that the wipeout fraction $F\left(T\right)\mathrm{}$ (i.e., the missing fraction of the integrated intensity of the NQR signal) represents the charge-stripe order parameter. The systematic study reveals bulk charge-stripe order throughout the superconducting region $0.07<~x<~\mathrm{0.25.}$ As a function of the reduced temperature $t\equiv {T/T}_{\mathrm{charge}},$ the temperature dependence of $F\left(t\right)\mathrm{}$ is sharpest for the hole concentration $x\sim 1/8,$ indicating that $x\sim 1/8$ is the optimum concentration for stripe formation.