Effect of Mn on the superconductivity of ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

We have prepared samples of ${\mathrm{YBa}}_2$(${\mathrm{Cu}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Mn}}_{\mathit{x}}$ ${)}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$, with x=0.0, 0.01, 0.025, 0.05, 0.075, 0.10, 0.15, and 0.20. Superconductivity with $T_c$ in the range 84–92 K is demonstrated by resistivity and magnetic susceptibility measurements. The substitution of Mn for Cu did not affect the onset temperature for the resistivity transition. X-ray diffraction analysis revealed the presence of additional phases, the amount increasing with Mn content, and also a slight modification of the ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ lattice parameters. A strong correlation between the width of the superconducting transition and the presence of additional phases was observed.