Ferromagnetic behavior and magnetic excitations in a molecular-based alternating-spin chain: Decamethylchromocenium tetracyanoethanide

We report the study of magnetic properties of a molecular-based alternating-spin chain: metallocenium electron-transfer salt decamethylchromocenium tetracyanoethanide, [${\mathrm{CrCp}}_2^{\mathrm{*}}$] [TCNE]. We give a modified spin-wave theory for the Heisenberg alternating-spin chains. The low-field susceptibility and magnetization data agree with the theoretical results indicating that one-dimensional linear magnon excitations dominate the magnetic behavior above the three-dimensional ordering temperature. Strong ferromagnetic intrachain coupling, J≃9 K, is found. Unusual critical phenomena associated with lattice dimensional crossover are discussed.