Concentration dependence of the electron-spin-resonance linewidth in ${\left(\mathrm{C}{\mathrm{H}}_3\right)}_4\mathrm{N}{\mathrm{Mn}}_{1-x}{\mathrm{Cu}}_x{\mathrm{Cl}}_3$

The electron-spin-resonance linewidth $\Delta H$ has been measured in ${\left(\mathrm{C}{\mathrm{H}}_3\right)}_4$NMn${\mathrm{Cl}}_3$ (TMMC) samples having a fraction $x$ of ${\mathrm{Cu}}^{++}$ substituted for ${\mathrm{Mn}}^{++}$, with $x$ up to 0.22. For the applied field along the chain axis, $\Delta H$ increases with $x$ in a manner consistent with predictions of one-dimensional spin dynamics.