We have systematically introduced spinless defects in the quasi-one-dimensional ferromagnetic system decamethylferrocenium tetracyanoethanide, [${\mathrm{FeCp}}_2^{\mathrm{*}}$][TCNE]. The three-dimensional ordering temperature ${\mathit{T}}_{\mathit{c}}$ decreases rapidly with the concentration of spinless sites. The rate of decrease of ${\mathit{T}}_{\mathit{c}}$ with concentration is in the order of the exchange spatial anisotropy (i.e., ${\mathit{J}}_{\mathrm{interchain}}$/${\mathit{J}}_{\mathrm{intrachain}}$) of the parent sysem in accordance with long-standing theoretical predictions.

• Received 5 May 1992

DOI:https://doi.org/10.1103/PhysRevB.46.6195