The influences of the packing ligand on spin state and magnetic interactions in new oxalates with 3d-transition metals

Abstract Two new hetero tri-nuclear oxalates (NH 4 ) 8 [Fe 2 Co(C 2 O 4 ) 8 ]·6H 2 O and [Fe 2 Co(C 2 O 4 ) 2 (OH) 4 ]·2H 2 O have been synthesized. The compound presented opposite behaviour in ac-susceptibility measurements, different frustration level and spin–orbit coupling in magnetization ones. The Mossbauer approach pointed to local interactions governed by metal-oxalate strongly coupled unit. The data were interpreted in terms of role of positive (NH 4 ) or negative (OH) bridging ligands on general magnetic properties.