Coexistence of, and Competition between, Superconductivity and Charge-Stripe Order in ${\mathrm{La}}_{1.6-\mathit{x}}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_{\mathit{x}}{\mathrm{CuO}}_4$

Previously we have presented evidence for stripe order of holes and spins in ${\mathrm{La}}_{1.6-x}{\mathrm{Nd}}_{0.4}{\mathrm{Sr}}_x{\mathrm{CuO}}_4$ with $x=0.12\mathrm{}$. Here we show, via neutron diffraction measurements of magnetic scattering, that similar order occurs in crystals with $x=0.15\mathrm{}$ and $0.20$. Zero-field-cooled magnetization measurements show that all three compositions are also superconducting, with the superconducting transition temperature increasing as the low-temperature staggered magnetization decreases. These results directly demonstrate an intimate connection between stripe correlations and superconductivity.